<PAGE>
 
                                                                  10(I)(L)(6)

                             WAIVER, AMENDMENT AND
                              EXTENSION AGREEMENT


    THIS WAIVER, AMENDMENT AND EXTENSION AGREEMENT ("Agreement"), dated as of
January 31, 1998, is made and entered into among SIGNATURE FINANCIAL/MARKETING,
INC. (the "Borrower") and the banks listed on the signature pages hereof
(herein, together with their respective successors and assigns, collectively
called the "Banks" and individually called a "Bank").

    WHEREAS, the Banks are parties to that certain Credit Agreement dated as of
September 27, 1996, as amended and restated as of October 21, 1996, and as
further amended or modified as of December 23, 1996, March 27, 1997, July 15,
1997, and August 29, 1997 (as heretofore amended or modified, the "Credit
Agreement"), among Signature Financial/Marketing, Inc., various Banks, The Bank
of New York as Documentation Agent, and The Bank of Nova Scotia, as
Administrative Agent; and

    WHEREAS, the Borrower desires to extend the Maturity Date of the Credit
Agreement from January 31, 1998, to July 31, 1998;

    NOW, THEREFORE, for valuable consideration, the receipt and adequacy of
which are hereby acknowledged, the parties hereto hereby agree as follows:



                                   ARTICLE I

                        WAIVER, AMENDMENT AND EXTENSION

    I.1   The Banks hereby waive an Event of Default (the "Specified Default")
arising solely by reason of the failure of the Borrower on January 31, 1998,
through the Effective Date of this Agreement to pay in full all Notes and other
Obligations.

    I.2   The Preamble to the Credit Agreement is hereby amended to add The Bank
of Nova Scotia as the Collateral Agent, and reads in its entirety as follows:

               This CREDIT AGREEMENT dated as of September 27, 1996, as amended
          and restated as of October 21, 1996 (the "Restatement Effective
          Date"), among Signature Financial/Marketing, Inc., a Delaware
          corporation (the "Borrower"), the banks listed on the signature pages
                            --------                                           
          hereof (herein, together and with their respective successors and
          assigns, collectively called the "Banks" and individually called a
          "Bank"), The Bank of New York ("BNY"), as documentation agent for the
          Banks (herein, in such capacity, together with its successors and
          assigns in such 
<PAGE>
 
          capacity, called the "Documentation Agent"), The Bank of Nova Scotia
          ("BNS"), as administrative agent to the Banks (herein in such
          capacity, together with its successors and assigns in such capacity,
          called the "Administrative Agent"), and BNS, as collateral agent for
          the Banks (herein, in such capacity, together with its successors and
          assigns in such capacity, called the "Collateral Agent") (the
          Documentation Agent, the Administrative Agent, and the Collateral
          Agent are herein collectively called the "Agents" and individually
          called an "Agent").

     I.3  Section 1.1 of the Credit Agreement is hereby amended by amending the
definition of "Guarantors," "Guaranty," and "Loan Documents," and by adding the
definitions of "Collateral Agent," "Pledge Agreements," "Pledged Securities,"
"Pledgors," and "Regulated Subsidiary" as follows:

               "Guarantors" means MW and each Subsidiary of the Borrower listed
                ----------                                                     
          on Schedule 1.1 hereto except that the term "Guarantors" when used in
             ------------                                                      
          Section 2.15 and clauses (c) and (i) of Section 7.4 shall be deemed
          not to include any Regulated Subsidiary or AM Industries, Inc.

               "Guaranty" means the guaranty executed by the Guarantors in
                --------                                                  
          substantially the form of Exhibit F-1, F-2, or F-3, as the same may be
                                    -----------  ---     ---                    
          amended or modified from time to time.

               "Loan Documents" means this Agreement, the Guaranties, the Pledge
                --------------                                                  
          Agreements, the Notes, and any fee letter and all other documents
          delivered to any Agent or any Bank in connection herewith.

               "Collateral Agent" means -- see Preamble.
                ----------------                        

               "Pledge Agreements" means those certain Pledge Agreements, dated
                -----------------                                              
          as of January 31, 1998, executed by Borrower and Montgomery Ward
          Enterprises, Inc., respectively, in favor of the Banks and the
          Collateral Agent, and granting to such Banks a first priority lien in
          the Pledged Securities, as collateral security for the repayment of
          the Obligations, each in substantially the form of Exhibit I-1, I-2,
                                                             -----------  --- 
          or I-3, as the same may be amended or modified from time to time.
             ---                                                           

               "Pledged Securities" shall have the meaning specified in Section
                ------------------                                             
          1 in the Pledge Agreements.

               "Pledgors" means Borrower and Montgomery Ward Enterprises, Inc.
                --------                                                      

               "Regulated Subsidiary" means any Subsidiary of the Borrower
                --------------------                                      
          listed on Schedule 1.1 hereto under the caption "Regulated
                    ------------                                    
          Subsidiaries."

                                       2
<PAGE>
 
     I.4  The words "calendar quarter" appearing in the fourth line of the first
sentence of the definition of "Interest Payment Date" in Section 1.1 of the
Credit Agreement is hereby changed to "calendar month."

     I.5  The Maturity Date is hereby extended by substituting "July 31, 1998"
for "January 31, 1998" in the definition of Maturity Date as set forth in
Section 1.1 of the Credit Agreement.

     I.6  Section 2.12 of the Credit Agreement is amended to read in its
entirety as follows:

               2.12 Extension Fee.  (a) Concurrent with the execution by each
                    -------------                                            
          Bank of the Waiver, Amendment and Extension Agreement dated as of
          January 31, 1998 ("Extension Agreement") among the Banks and the
          Borrower, the Borrower agrees to pay directly to each Bank in
          immediately available funds a fee equal to 1/8th% of the aggregate
          outstanding principal amount of the Loans then outstanding from each
          Bank (it being understood that such fee shall be retained by such Bank
          regardless of whether the Extension Agreement becomes effective).

               (b)  The Borrower agrees to pay to the Administrative Agent in
          immediately available funds, for the prorata account of each Bank, a
          fee of $2,000 per day for each day the Loans (or any principal amount
          thereof) remain outstanding during the month of June 1998.  Such fee
          shall be payable on the earlier of the day all the Loans are repaid in
          full or June 30, 1998.

     I.7  Article II of the Credit Agreement is amended by adding the following
Sections 2.13, 2.14, 2.15, and 2.16 thereto:

               2.13 Subsidiary Guaranties.  Each of the Subsidiary Guarantors
                    ---------------------                                    
          identified on Schedule 1.1 have executed and delivered, or are
          executing and delivering, to the Banks either a Guaranty (Non-
          Insurance Subsidiaries) or a Guaranty (Regulated Subsidiaries), as
          indicated on Schedule 1.1, in the form of Exhibits F-2 and F-3,
                       ------------                 -------------    --- 
          respectively.

               2.14 Pledge of Securities.  Borrower and Montgomery Ward
                    --------------------                               
          Enterprises, Inc. are executing and delivering to the Banks the Pledge
          Agreements, in the form of Exhibits I-1, I-2, or I-3.
                                     ------------  ---     --- 

               2.15 Additional Collateral.  Borrower and each Subsidiary
                    ---------------------                               
          Guarantor except AM Industries Inc. (formerly known as Amoco Motor
          Club, Inc.) shall furnish Banks with such additional guaranties,
          collateral, and credit enhancement as the Banks may request from time
          to time.

               2.16 Collateral Agent.  The Collateral Agent will have such
                    ----------------                                      
          duties as are set 

                                       3
<PAGE>
 
          forth in that certain Collateral Agent Agreement, dated as of January
          31, 1998, among BNY, BNS, and the Collateral Agent.

     I.8  Section 5.3 of the Credit Agreement is amended by adding the phrase
"and the Pledge Agreements" after the words "Section 6.13" and before the comma.

     I.9  Section 7.8(d) of the Credit Agreement is amended to read in its
entirety as follows:

               (d)  the Pledge Agreement executed by Montgomery Ward
          Enterprises, Inc. and the Guaranties.

     I.10 Sections 8.1(m) and 8.1(r) of the Credit Agreement are amended to read
in their entirety as follows:

               (m)  Guarantor or Pledgor Defaults.  Any Guarantor or Pledgor
                    -----------------------------                           
          fails in any material respect to perform or observe any term, covenant
          or agreement in its Guaranty or Pledge Agreement, as applicable; or
          the Guaranty of any Guarantor or the Pledge Agreement of any Pledgor
          is for any reason partially (including, with respect to future
          advances) or wholly revoked or invalidated, or otherwise ceases to be
          in full force and effect, or any Guarantor, Pledgor, or any other
          Person contests in any manner the validity or enforceability of such
          Guaranty or Pledge Agreement or denies that it has any further
          liability or obligation thereunder; or any event described in
          subsections (f) or (g) of this Section occurs with respect to any
          Guarantor or Pledgor.

               (r)  Citicorp Commitment Letter.  (i) Any party to that certain
                    --------------------------                                
          Commitment Letter, dated as of March 24, 1998, between Citicorp USA,
          Inc. and the Borrower, as extended by letter agreement dated May 6,
          1998 (the "Commitment Letter") revokes, withdraws, or terminates the
          Commitment Letter, or (ii) any amendment, modification or waiver is
          made to the Commitment Letter which is not acceptable to the Banks, or
          (iii) the Commitment Letter shall cease to be in full force and
          effect.

     I.11 Schedule 1.1 of the Credit Agreement is hereby amended and replaced in
its entirety with Schedule 1.1 attached hereto, and new Exhibits F-3., I-1, I-2,
                                                        ------------   ---  --- 
and I-3 are hereby added to the Credit Agreement in the form of Exhibits F-3, I-
    ---                                                         ------------  -
1, I-2, and I-3 attached hereto.
-  ---      ---                 

     I.12 Schedules 5.5, 5.7, 5.11, 5.12, 5.16(a), 5.16(b), and 5.17 are each
          -------------  ---  ----  ----  -------  -------      ----         
hereby amended by adding thereto the items set forth in the applicable section
of Schedule J attached hereto.
   ----------                 

     I.13 Notwithstanding the provisions of Section 2.4 of the Credit Agreement,
from and after January 31, 1998, Borrower shall not be entitled to elect to
convert any Base Rate Loans to 

                                       4
<PAGE>
 
LIBO Rate Loans, and any LIBO Rate Loans outstanding on January 31, 1998, shall,
effective as of the end of the applicable Interest Period, be converted into
Base Rate Loans.

     I.14 Notwithstanding the provisions of Section 2.7 of the Credit Agreement,
for the period from January 31, 1998, until May 31, 1998, interest on the unpaid
principal amount shall accrue and be payable at a rate per annum equal to the
sum of two percent (2%) per annum plus the rate otherwise in effect pursuant to
Section 2.7(a) of the Credit Agreement; and from and after June 1, 1998,
interest on the unpaid principal amount shall accrue and be payable pursuant to
Section 2.7(a)(i) of the Credit Agreement, except that if an Event of Default
exists after the Effective Date of this Agreement, then interest on the unpaid
principal amount shall accrue and be payable pursuant to Section 2.7(c) of the
Credit Agreement.

     I.15 The waiver, amendment and extension contained herein are limited
precisely to their terms and shall not constitute a waiver, amendment or other
modification generally or for any other purpose.


                                  ARTICLE II

                        REPRESENTATIONS AND WARRANTIES
                                        
    The Borrower hereby represents and warrants to the Agents and the Banks as
follows:

    II.1  No Default.  No Default or Event of Default has occurred and is
          ----------                                                     
continuing, other than the Specified Default, or will exist after giving effect
to this Agreement.

    II.2  Due Execution.  The execution, delivery and performance of this
          -------------                                                  
Agreement, (i) are within the Borrower's corporate powers, (ii) have been duly
authorized by all necessary corporate action, (iii) do not require any
governmental approval which has not been previously obtained (and each such
governmental approval that has been previously obtained remains effective), (iv)
do not and will not contravene or conflict with any provision of law, or of any
judgment, decree or order, or of the Borrower's charter or by-laws, and (v) do
not and will not contravene or conflict with, or cause any Lien to arise under,
any provision of any agreement binding upon the Borrower, any Subsidiary or any
of their respective properties.

    II.3  Validity.  The Credit Agreement as extended by this Agreement
          --------                                                     
constitutes the legal, valid and binding obligations of the Borrower,
enforceable against it in accordance with its respective terms, without defense,
counterclaim or offset.

    II.4  Credit Agreement.  All representations and warranties of the Borrower
          ----------------                                                     
contained in Article 5 (except Section 5.11(b) of the Credit Agreement) are true
             ---------         ---------------                                  
and correct as of the date hereof with the same effect as though made on the
date hereof.  Since December 31, 1995, there has not occurred any event which
(i) materially impairs the ability of the Borrower to perform its 

                                       5
<PAGE>
 
obligations under any Loan Document or to avoid, after the Effective Date
hereof, any Event of Default, or (ii) materially adversely effects the legality,
validity, binding effect or enforceability against the Borrower of any Loan
Document.

                                  ARTICLE III

                                    GENERAL

    III.1  Expenses.  The Borrower agrees to pay all fees and expenses of each
           --------                                                           
of the Agents and the Banks (including all legal fees and related expenses of
separate counsel for each of the Banks and the Agents) in connection with the
preparation, execution and delivery of this Agreement.

    III.2  Effectiveness.  This Agreement shall become effective on the date
           -------------                                                    
(the "Effective Date") on which the Administrative or Collateral Agent shall
have received each of the following:

     (a)   Agreements.  Counterparts of this Agreement, the Guaranty of each
           ----------                                                       
           Subsidiary Guarantor, and the Pledge Agreements, whether on the same
           or different counterparts, executed by the Borrower, the Subsidiary
           Guarantors, and the Pledgors, as appropriate, and by the Required
           Banks (or in the case of any Bank as to which an executed counterpart
           shall not have been so received, telegraphic, telefax, telex or other
           written confirmation of execution of a counterpart hereof by such
           Bank);

     (b)   MW Court Order.  The entry of an order by the United States
           --------------
           Bankruptcy Court, District of Delaware, In Re Montgomery Ward Holding
           Corp., a Delaware corporation, et al., Case No. 97-1409 (PJW)
           substantially in the form attached hereto as Exhibit X, or the
                                                        ---------
           written waiver of this requirement by the Banks;

     (c)   Agreement Fee.  Evidence of payment from the Borrower to each Bank of
           -------------                                                        
           the fees provided for in Section 2.12 of the Credit Agreement as
           herein amended; and

     (d)   Pledged Securities.  All stock certificates evidencing the Pledged
           ------------------                                                
           Securities, all financing statements relating thereto, and all stock
           powers relating thereto executed by Pledgors.

     (e)   Legal Opinions.  Favorable opinions of counsel of Borrower and its
           --------------                                                    
           subsidiaries, in form and substance acceptable to the Banks, opining
           on the enforceability of this Agreement, the Guaranty of each
           Subsidiary Guarantor, and the Pledge Agreements.

                                       6
<PAGE>
 
    III.3  Definitions.  Except as otherwise herein specifically defined, all
           -----------                                                       
the capitalized terms contained herein shall have the meaning ascribed to such
terms in the Credit Agreement.

    III.4  Reaffirmation.  Except as hereinabove expressly provided, all the
           -------------                                                    
terms and provisions of the Credit Agreement shall remain in full force and
effect and all references therein and in any related documents to the Credit
Agreement shall henceforth refer to the Credit Agreement as extended by this
Agreement.  This Agreement shall be deemed incorporated into, and a part of, the
Credit Agreement.

    III.5  Successors.  This Agreement shall be binding upon and inure to the
           ----------                                                        
benefit of, the parties hereto and their respective successors and assigns.

    III.6  Governing Law.  This Agreement shall be governed by and construed in
           -------------                                                       
accordance with the laws of the State of Illinois.

    III.7  Counterparts.  This Agreement may be executed in any number of
           ------------                                                  
counterparts and by the different parties on separate counterparts and each such
counterpart shall be deemed to be an original, but all such counterparts shall
together constitute but one and the same agreement.

    Dated at Chicago, Illinois as of the date, month and year first above
written but executed and delivered on or after June 26, 1998.


                                      SIGNATURE FINANCIAL/MARKETING, INC.
                                
                                
                                      By:   /s/ John Workman
                                            ---------------------------------
                                      Name: Acting Chief Financial Officer
                                            ---------------------------------

ACCEPTED AND APPROVED:

THE BANK OF NEW YORK, in its
individual capacity and in its
capacity as Documentation Agent


By:  /s/ Julie B. Follosco
     ----------------------------
Name:  Vice President
     ----------------------------

                                       7
<PAGE>
 
THE BANK OF NOVA SCOTIA, in its
individual capacity, in its capacity
as Administrative Agent and in its
capacity as Collateral Agent


By:   /s/ D.N. Gillespie
      -------------------------------
Name: Assistant General Manager
      -------------------------------

                                       8
<PAGE>
 
REAFFIRMATION OF GUARANTY:

     Each Guarantor hereby confirms and agrees that (i) its Guaranty dated as of
September 27, 1996, as heretofore reaffirmed from time to time, is, and shall
continue to be in full force and effect and is hereby ratified and confirmed in
all respects, as applied to the Credit Agreement as modified above; (ii) to the
extent the liability of any Guarantor under its Guaranty is limited by
applicable law, such Guarantor shall be nonetheless liable under its Guaranty to
the maximum extent permitted by applicable law, and (iii) to the extent that a
Guarantor shall have paid more than its proportionate share of any payment made
under its Guaranty, such Guarantor shall be entitled to seek and receive
contribution from and against any other Guarantor which has not paid its
proportionate share of such payment (it being understood that (a) such
Guarantor's right of contribution shall be subordinated to the obligations of
such Guarantor to the Banks and shall not be paid until all of the Obligations
under the Credit Agreement have been indefeasibly paid in full, and (b) the
provisions of this clause (iii) shall in no respect limit the obligations and
liabilities of any Guarantor to the Banks, and each Guarantor shall remain
liable to the Banks for the full amount guaranteed by such Guarantor under its
Guaranty).

CREDIT CARD SENTINEL, INC.
ISS AGENCY, INC.
MONTGOMERY WARD CLUBS, INC.
MONTGOMERY WARD ENTERPRISES, INC.
SIGNATURECARD, INC.
MONTGOMERY WARD FINANCIAL CENTER, INC.
MONTGOMERY WARD AGENCY, INC.
NATIONAL DENTAL SERVICE, INC.
SIGNATURE DIRECT, INC.
SIGNATURE INVESTMENT ADVISORS, INC.
AM INDUSTRIES, INC.  (FORMERLY KNOWN AS AMOCO MOTOR CLUB, INC.)


By:   /s/ John Workman
      ---------------------------------------
Name: Acting Chief Financial Officer
      ---------------------------------------

                                       9
<PAGE>
 
                                 SCHEDULE 1.1
                                 ------------

                            GUARANTOR SUBSIDIARIES
                            ----------------------


A.   Non-Insurance Subsidiaries:
     -------------------------- 
     1.   Credit Card Sentinel, Inc.                                   
     2.   ISS Agency, Inc.                                             
     3.   Montgomery Ward Clubs, Inc.                                  
     4.   Montgomery Ward Enterprises, Inc.                            
     5.   SignatureCard, Inc.                                          
     6.   Montgomery Ward Financial Center, Inc.                       
     7.   Montgomery Ward Agency, Inc.                                 
     8.   National Dental Service, Inc.                                
     9.   Signature Direct, Inc.                                       
     10.  Signature Investment Advisors, Inc.                          
     11.  AM Industries, Inc., formerly known as Amoco Motor Club, Inc. 

B.   Regulated Subsidiaries:
     ---------------------- 
     1.   Montgomery Ward Auto Club, Inc.         
     2.   Greater California Dental Plan          
     3.   Signature Dental Plan of Florida, Inc.  
     4.   Ocoma Industries, Inc.                  
     5.   Signature's Nationwide Auto Club, Inc.  
     6.   Signature Agency, Inc.                  
     7.   Signature Agency - Wyoming, Inc.        
     8.   AEC Signature Industries, Limited        

                                       10