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                                                                 EXHIBIT 10.12.1

                               FIRST AMENDMENT TO
              FIRST AMENDED AND RESTATED REVOLVING CREDIT AGREEMENT


         THIS FIRST AMENDMENT TO FIRST AMENDED AND RESTATED REVOLVING CREDIT
AGREEMENT, dated effective as of October 15, 1999 (the "First Amendment"), is
entered into between and among HERITAGE SERVICE CORP., a Delaware corporation
(the "Borrower") and BANK OF OKLAHOMA, NATIONAL ASSOCIATION ("BOk"), MERCANTILE
BANK NATIONAL ASSOCIATION ("Mercantile") and LOCAL OKLAHOMA BANK, N. A.
("Local") (BOk, Firstar, Mercantile and Local collectively referred to herein as
the "Banks"), BOk, as administrative agent for the Banks (in such capacity, the
"Administrative Agent") and Mercantile, as co-agent for the Banks (in such
capacity, the "Co-Agent").

         WHEREAS, the Borrower, the Banks, the Administrative Agent and the
Co-Agent entered into that certain First Amended and Restated Credit Agreement
dated as of May 31, 1999, (the "Credit Agreement"); and

         WHEREAS, due to certain modifications and amendments to the Operating
Partnership Credit Agreement (as defined in the Credit Agreement), including an
increase in the maximum outstanding amount of the Working Capital Loan pursuant
to the Working Capital Facility from $20,000,000.00 to $35,000,000.00, and
reallocation of the Percentage Interests of the respective Banks, the Borrower,
the Banks, the Administrative Agent and the Co-Agent desire to amend and modify
certain provisions of the Credit Agreement concerning such matters and the
increase in interest rates.

         NOW THEREFORE, the Credit Agreement is hereby amended and modified as
follows:

         1. The definition of "Applicable Margin" in Schedule I of the Credit
Agreement is deleted in its entirety and replaced with the following:

                  "Applicable Margin". With respect to any Eurodollar Loan or
         with respect to any Base Rate Loan, the rate of interest per annum
         determined for any Margin Period:

                           (i) if the Leverage Ratio on the Financial Statement
                  Delivery Date commencing such Margin Period was less than 3.25
                  to 1, the Applicable Margin will be .875% for Eurodollar Loans
                  and zero for Base Rate Loans;

                           (ii) if the Leverage Ratio on the Financial Statement
                  Delivery Date commencing such Margin Period was equal to or
                  greater than 3.25 to 1 but less than 3.75 to 1, the Applicable
                  Margin will be 1.125% for Eurodollar Loans and zero for Base
                  Rate Loans;

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                           (iii) if the Leverage Ratio on the Financial
                  Statement Delivery Date commencing such Margin Period was
                  equal to or greater than 3.75 to 1 but less than 4.25 to 1,
                  the Applicable Margin will be 1.375% for Eurodollar Loans and
                  zero for Base Rate Loans;

                           (iv) if the Leverage Ratio on the Financial Statement
                  Delivery Date commencing such Margin Period was equal to or
                  greater than 4.25 to 1 but less than 4.50 to 1, the Applicable
                  Margin will be 1.500% for Eurodollar Loans and zero for Base
                  Rate Loans;

                           (v) if the Leverage Ratio on the Financial Statement
                  Delivery Date commencing such Margin Period was equal to or
                  greater than 4.50 to 1 but less than 4.75 to 1, the Applicable
                  Margin will be 1.625% for Eurodollar Loans and 0.125% for Base
                  Rate Loans; and

                           (vi) if the Leverage Ratio on the Financial Statement
                  Delivery Date commencing such Margin Period was equal to or
                  greater than 4.75 to 1, the Applicable Margin will be 1.875%
                  for Eurodollar Loans and .250% for Base Rate Loans.

                  Notwithstanding the foregoing, if any of the financial
         statements required pursuant to Section 7A.1(i) of the Operating
         Partnership Credit Agreement are not delivered within the time periods
         specified in Section 7A.1(i), the Applicable Margin shall be the
         Applicable Margin set forth in clause (vi) above until the date such
         financial statements are delivered.

         2. The definition of "Existing Credit Agreement" in the Credit
Agreement is deleted in its entirety and replaced with the following:

                  "Operating Partnership Credit Agreement" means the First
         Amended and Restated Credit Agreement dated as of May 31, 1999, between
         and among Heritage Operating, L.P., a Delaware limited partnership,
         BOk, Mercantile and Local, and BOk, as Administrative Agent, and
         Mercantile, as Co-Agent, as amended by the First Amendment thereto
         dated as of October 15, 1999, and as further amended and modified from
         time to time.

         3. Section 2.1.2(ii) of the Credit Agreement is amended by deleting
"$20,000,000" and inserting in lieu thereof "$35,000,000." The form of Exhibit
2.1.4 (Revolver Notes) annexed to the Credit Agreement is replaced with the form
of Exhibit 2.1.4 annexed to this First Amendment.

         4. Article III of the Credit Agreement is amended by deleting "June 30,
1999" and inserting in lieu thereof "October 31, 1999."

         5. Section 7B.1(i) of the Existing Credit Agreement is amended by
deleting "$20,000,000" and inserting in lieu thereof "$35,000,000."


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         6. Section 10.1 of the Existing Credit Agreement is deleted in its
entirety and replaced by the following:

                  10.1 Interests in Loans/Commitments. The percentage interest
         of each Bank in the Loans and the Commitments, shall be computed based
         on the maximum principal amount for each Bank as follows:

<Table>
<Caption>

                                  MAXIMUM REVOLVER
                                  LOAN COMMITMENT            PERCENTAGE
                   BANK              AMOUNT                   INTEREST
                   ----           ----------------           ----------
<S>                               <C>                        <C>
                    BOk            $  529,411.00              52.9411%
                Mercantile            294,118.00              29.4118%
                   Local              176,471.00              17.6471%
                                   -------------             --------

                   Total           $1,000,000.00             100.0000%
                                   =============             ========
</Table>

                  The foregoing percentage interests, as from time to time in
         effect and reflected in the Register, are referred to as the
         "Percentage Interests" with respect to all or any portion of the Loans
         and Letters of Credit, and the Commitments.

         7. Credit Agreement/Counterparts. All of the remaining terms,
provisions and conditions of the Credit Agreement, except as otherwise expressly
amended and modified by this First Amendment, shall continue in full force and
effect in all respects. This First Amendment may be executed in multiple
counterparts, each of which shall be deemed an original and all of which shall
constitute a single First Amendment. Delivery of an executed counterpart of a
signature page to this Agreement by telecopier shall be as effective as delivery
of a manually executed counterpart of this Agreement.

         8. Further Assurances. The Borrower will, upon the request of the Agent
from time to time, promptly execute, acknowledge and deliver, and file and
record, all such instruments and notices, and take all such action, as the Agent
deem necessary or advisable to carry out the intent and purposes of this First
Amendment and the Credit Agreement.

         9. General. The Credit Agreement and all of the other Loan Documents
are each confirmed as being in full force and effect. This First Amendment, the
Credit Agreement and the other Loan Documents referred to herein or therein
constitute the entire understanding of the parties with respect to the subject
matter hereof and thereof and supersede all prior and current understandings and
agreements, whether written or oral, with respect to such subject matter. The
invalidity or unenforceability of any provision hereof shall not affect the
validity and enforceability of any other term or provision hereof. The headings
in this First Amendment are for convenience of reference only and shall not
alter, limit or otherwise affect the meaning hereof. Each of this First
Amendment and the Credit Agreement is a Loan Document and may be executed in any
number of counterparts, which together shall constitute one instrument, and
shall bind and inure to the benefit of the parties and their respective
successors and assigns including as such successors and assigns all holders of
any Note. This First Amendment shall be


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governed by and construed in accordance with the laws (other than the conflict
of law rules) of the State of Oklahoma.

         IN WITNESS WHEREOF, the parties hereto have caused this First Amendment
to Amended and Restated Credit Agreement to be duly executed and delivered in
Tulsa, Oklahoma, effective as of the 15th day of October, 1999, by the
undersigned duly authorized officers thereof.


                                 "Borrower"

                                 HERITAGE SERVICE CORP.,
                                 a Delaware corporation


                                 By
                                   ----------------------------------------
                                   H. Michael Krimbill, President


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                                 "Banks"

                                 BANK OF OKLAHOMA, NATIONAL
                                 ASSOCIATION


                                 By
                                   ----------------------------------------
                                   Denise L. Maltby, Senior Vice President



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                                 MERCANTILE BANK NATIONAL ASSOCIATION


                                 By
                                   ----------------------------------------
                                   Jeffrey A. Nelson, Vice President



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                                 LOCAL OKLAHOMA BANK, N.A.


                                 By
                                   ----------------------------------------
                                   Elisabeth F. Blue, Senior Vice President





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                                 "Administrative Agent"

                                 BANK OF OKLAHOMA, NATIONAL
                                 ASSOCIATION


                                 By
                                   ----------------------------------------
                                   Denise L. Maltby, Senior Vice President



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                                 "Co-Agent"

                                 MERCANTILE BANK NATIONAL ASSOCIATION


                                 By
                                   ----------------------------------------
                                   Jeffrey A. Nelson, Vice President