<PAGE>

                                                                     EXHIBIT 4.4

                   ASSUMPTION AGREEMENT AND FIRST AMENDMENT TO
                      CONTRIBUTION AND SERVICING AGREEMENT


         This ASSUMPTION AGREEMENT AND FIRST AMENDMENT TO CONTRIBUTION AND
SERVICING AGREEMENT (the "Agreement") dated as of January 31, 2001 is entered
into among Green Tree Lease Finance 1998-1, LLC, a Delaware limited liability
company ("Issuer"), Green Tree Lease Finance II, Inc., a Minnesota corporation
(the "Contributor"), Conseco Finance Vendor Services Corporation, a Delaware
corporation formerly known as Green Tree Vendor Services Corporation (in its
individual capacity, "Vendor Services," and in its capacity as Servicer, the
"Servicer"), U.S. Bank Trust National Association, a national banking
association (the "Trustee"), WFFLI Lease Finance 1998-1, LLC, a Delaware limited
liability company (the "Successor Issuer"), WFFLI Lease Finance II, LLC, a
Delaware limited liability company (the "Successor Contributor"), and Wells
Fargo Financial Leasing, Inc., an Iowa corporation (the "Successor Servicer").

         WHEREAS, the Issuer, the Contributor, Vendor Services (both
individually and in its capacity as the Servicer) and the Trustee are parties to
a Contribution and Servicing Agreement dated as of December 1, 1998 (the
"Contribution and Servicing Agreement").

         WHEREAS, pursuant to an Asset Purchase Agreement dated as of December
8, 2000 by and among the Successor Servicer, Conseco, Inc., Conseco Finance
Corp., Vendor Services, the Contributor, the Issuer and Conseco Finance Lease
2000-1, LLC (the "Purchase Agreement"), Successor Servicer has agreed to
purchase substantially all of the assets and certain liabilities of Vendor
Services and to assume all of the obligations of Vendor Services as Servicer
under the Contribution and Servicing Agreement.

         WHEREAS, pursuant to the Purchase Agreement, Successor Servicer will
cause the Successor Contributor, a limited liability company of which the
Successor Servicer is the sole member, to purchase substantially all of the
assets of Contributor and to assume all of the obligations of Contributor under
the Contribution and Servicing Agreement.

         WHEREAS, pursuant to the terms of a Supplemental Indenture dated as of
the date hereof to the Indenture dated as of December 1, 1998 between the Issuer
and the Trustee relating to the 5.201% Lease-Backed Notes, Class A-1, 5.55%
Lease-Backed Notes, Class A-2, 5.60% Lease-Backed Notes, Class A-3, 5.74%
Lease-Backed Notes, Class A-4, 6.66% Lease-Backed Notes, Class B, and 7.63%
Lease-Backed Notes, Class C of the Issuer (as so supplemented, the "Indenture"),
Successor Issuer shall succeed as issuer under the Indenture.

         WHEREAS, pursuant to the terms of the Contribution and Servicing
Agreement, neither the Contributor nor the Servicer shall permit any other
Person to become the successor to its respective business unless certain
conditions set forth in the Contribution and Servicing Agreement are satisfied,
including the requirement that any such successor shall execute an assumption
agreement assuming the obligations of the Contributor or the Servicer, as the
case may be, under the Contribution and Servicing Agreement.
<PAGE>

         WHEREAS, the Contributor and the Servicer have furnished the Issuer and
the Trustee with (i) a certificate of a Responsible Officer and an Opinion of
Counsel stating that the agreements of assumption by the Successor Contributor
and the Successor Servicer contained herein comply with Sections 6.2 and 7.2,
respectively, of the Contribution and Servicing Agreement and that all
conditions precedent in the Contribution and Servicing Agreement relating to
such successions have been complied with; and (ii) an Opinion of Counsel stating
that all financing statements and continuation statements and amendments have
been executed and filed that are necessary to preserve and protect the interest
of the Issuer in the Trust Assets.

         WHEREAS, the parties hereto desire to amend certain provisions of the
Contribution and Servicing Agreement simultaneously with the Successor
Contributor and the Successor Servicer entering into such agreements of
assumption.

         WHEREAS, pursuant to Section 10.1(a) of the Contribution and Servicing
Agreement, the Contribution and Servicing Agreement may be amended without the
consent of any of the Noteholders (i) to cure any ambiguity contained therein,
(ii) to correct or supplement any provisions in the Contribution and Servicing
Agreement that may be inconsistent with any other provision therein; or (iii) to
make any other provisions with respect to matters or questions arising under the
Contribution and Servicing Agreement that are not inconsistent with the
provisions thereof; provided, however, that such action shall not, as evidenced
by an Opinion of Counsel, adversely affect in any material respect the interests
of the Noteholders.

         WHEREAS, an Opinion of Counsel has been delivered stating that the
amendments to the Contribution and Servicing Agreement contained herein shall
not adversely affect in any material respect the interests of the Noteholders.

         NOW, THEREFORE, in consideration of covenants and agreements contained
herein and other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the parties hereby agree as follows:


                                    ARTICLE I
                                    ---------

                AMENDMENT TO CONTRIBUTION AND SERVICING AGREEMENT
                -------------------------------------------------

         Section 1.1. Defined Terms. Certain definitions set forth in Section
1.1 of the Contribution and Servicing Agreement are hereby amended to read as
follows:

         Transfer Agreement: The Transfer Agreement, dated as of December 1,
         1998, between Vendor Services and the Contributor, as the same may be
         amended or supplemented from time to time.

         Vendor Services: Conseco Finance Vendor Services Corporation, a
         Delaware corporation, or its successor in interest."


         Section 1.2. Organizational Representations. Throughout the
Contribution and Servicing Agreement, all references to a "corporation" shall be
deemed to include a limited

                                      -2-
<PAGE>

liability company; all references to "corporate action" shall be deemed to
include the actions of a limited liability company; all references to
"incorporated" shall be deemed to include being organized as a limited liability
company; all references to "articles of incorporation" or "bylaws" shall be
deemed to include the equivalent organizational documents of a limited liability
company; all references to "stockholder" or "stockholders" shall be deemed to
include a member or members of a limited liability company; the reference in
Section 2.4(a) to the Contributor's good standing "under the laws of the State
of Minnesota" shall be revised to "under the laws of its jurisdiction of
organization"; and any such other changes shall be deemed to have been made as
are necessary to allow a limited liability company to serve as the Contributor
under the Contribution and Servicing Agreement to the same extent as it would be
able to serve if it were organized as a corporation.


                                   ARTICLE II
                                   ----------

                      ASSIGNMENT AND ASSUMPTION AGREEMENTS
                      ------------------------------------

         Section 2.1. Successor Contributor. The Contributor hereby grants,
assigns, transfers and conveys to the Successor Contributor its entire right,
title and interest in, to and under the Contribution and Servicing Agreement and
Related Documents. The Successor Contributor hereby accepts the foregoing
assignment and hereby assumes and agrees to perform all of the obligations of
the Contributor under the Contribution and Servicing Agreement and each of the
Related Documents. The Successor Contributor further agrees to indemnify, defend
and hold harmless the Contributor against and from any loss, liability or
expense arising in connection with the Successor Contributor's failure to
perform such obligations on and after the date hereof.

         Section 2.2. Assumption of Successor Servicer. The Servicer hereby
grants, assigns, transfers and conveys to Successor Servicer its entire right,
title and interest in, to and under the Contribution and Servicing Agreement and
Related Documents. Successor Servicer hereby accepts the foregoing assignment
and hereby assumes and agrees to perform all of the obligations of the Servicer
under the Contribution and Servicing Agreement and each of the Related
Documents. Successor Servicer further agrees to indemnify, defend and hold
harmless Servicer against and from any loss, liability or expense arising in
connection with Successor Servicer's failure to perform such obligations on and
after the date hereof.

         Section 2.3. Notice of Successor Servicer. The Trustee hereby agrees to
give prompt written notice of appointment of Successor Servicer as Servicer
under the Contribution and Servicing Agreement to the Noteholders.


                                   ARTICLE III
                                   -----------

                                  MISCELLANEOUS
                                  -------------

         Section 3.1. Defined Terms. Defined terms used herein and not otherwise
defined herein shall have the meanings assigned to them in the Contribution and
Servicing Agreement or, if not defined therein, in the Indenture.

                                      -3-
<PAGE>

         Section 3.2. Ratification of Contribution and Servicing Agreement.
Except as expressly amended by this Agreement, the Contribution and Servicing
Agreement is in all respects ratified and confirmed and all the terms,
conditions and provisions thereof shall remain in full force and effect.

         Section 3.3. Entire Agreement. This Agreement (including the exhibits,
schedules and other documents referred to herein) contains the entire
understanding between the parties hereto with respect to the subject matter
hereof and supersedes any prior understandings, agreements or representations,
written or oral, relating to the subject matter hereof.

         Section 3.4. Counterparts. This Agreement may be executed in separate
counterparts, each of which will be an original and all of which taken together
shall constitute one and the same agreement, and any party hereto may execute
this Agreement by signing any such counterpart.

         Section 3.5. Severability. Whenever possible, each provision of this
Agreement shall be interpreted in such a manner as to be effective and valid
under applicable law but if any provision of this Agreement is held to be
invalid, illegal or unenforceable under any applicable law or rule, the
validity, legality and enforceability of the other provision of this Agreement
will not be affected or impaired thereby.

         Section 3.6. Modification, Amendment, Waiver or Termination. No
provision of this Agreement may be modified, amended, waived or terminated
except by an instrument in writing signed by the parties to this Agreement. No
course of dealing between the parties will modify, amend, waive or terminate any
provision of this Agreement or any rights or obligations of any party under or
by reason of this Agreement.

         Section 3.7. Headings. The headings and any table of contents contained
in this Agreement are for reference purposes only and shall not in any way
affect the meaning or interpretation of this Agreement.

         Section 3.8. Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF MINNESOTA WITHOUT REGARD
TO THE PRINCIPLES OF CONFLICTS OF LAWS THEREOF AND THE OBLIGATIONS, RIGHTS AND
REMEDIES OF THE PARTIES UNDER THIS AGREEMENT SHALL BE DETERMINED IN ACCORDANCE
WITH SUCH LAWS.

         Section 3.9. Further Assurances. Each party agrees that at any time,
and from time to time, it will do all such things and execute and deliver all
such instruments, assignments, releases, financing statements, continuation
statements, other documents and assurances as any other party reasonably deems
necessary or desirable to carry out the intent, purpose and conditions of this
Agreement, the Related Documents and the transactions contemplated hereby and
thereby.

                                      -4-
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed, all as of the first day and year first written above.



                                     GREEN TREE LEASE FINANCE 1998-1, LLC



                                     By: /s/ Brian F. Corey
                                         ---------------------------------------
                                     Name: Brian F. Corey
                                     Title: Senior Vice President and Secretary



                                     GREEN TREE LEASE FINANCE II, INC.



                                     By: /s/ Brian F. Corey
                                         ---------------------------------------
                                     Name: Brian F. Corey
                                     Title: Senior Vice President and Secretary




                                     CONSECO FINANCE VENDOR SERVICES CORPORATION



                                     By: /s/ Brian F. Corey
                                         ---------------------------------------
                                     Name: Brian F. Corey
                                     Title: Senior Vice President and Secretary




                                     U.S. BANK TRUST NATIONAL ASSOCIATION


                                     By: /s/ Tamara Schultz-Fugh
                                         ---------------------------------------
                                     Name: Tamara Schultz-Fugh
                                     Title: Vice President

                                       -5-
<PAGE>

                                     WFFLI LEASE FINANCE 1998-1, LLC


                                     By: /s/ Steve R. Wagner
                                         ---------------------------------------
                                     Name: Steve R. Wagner
                                     Title: President



                                     WFFLI LEASE FINANCE II, LLC



                                     By: /s/ Steve R. Wagner
                                         ---------------------------------------
                                     Name: Steve R. Wagner
                                     Title: President



                                     WELLS FARGO FINANCIAL LEASING, INC.



                                     By: /s/ Steve R. Wagner
                                         ---------------------------------------
                                     Name: Steve R. Wagner
                                     Title: Vice President

                                      -6-