<PAGE>

                                                                   Exhibit 10.28

                               AMENDMENT NO. 1 TO
                          SALE AND SERVICING AGREEMENT

     AMENDMENT NO. 1 (this "Amendment"), dated as of March 30, 2001, to the SALE
                            ---------
AND SERVICING AGREEMENT, dated as of September 14, 2000, by and among
AMERICREDIT MANHATTAN TRUST, a Delaware business trust (the "Borrower"),
                                                             --------
AMERICREDIT FINANCIAL SERVICES, INC., a Delaware corporation ("AFS"), as a
                                                               ---
seller and as servicer (in such capacities, the "Primary Seller" and the
                                                 --------------
"Servicer", respectively), AMERICREDIT FUNDING CORP. V, a Delaware corporation,
 --------
as a seller (the "Secondary Seller," and, together with the Primary Seller, the
                  ----------------
"Sellers," and each, a "Seller"), and THE CHASE MANHATTAN BANK, a New York
 -------                ------
banking corporation ("Chase"), as backup servicer and as administrative agent
                      -----
(in such capacities, the "Backup Servicer" and the "Administrative Agent,"
                          ---------------           --------------------
respectively).


                                  WITNESSETH:


     WHEREAS, the Borrower, the Sellers, the Servicer, the Backup Servicer and
the Administrative Agent have entered into a Sale and Servicing Agreement, dated
as of September 14, 2000 (the "Agreement");
                               ---------

     WHEREAS, the parties hereto wish to amend the Agreement as hereinafter
provided.

     NOW, THEREFORE, in consideration of the foregoing and of the mutual
covenants herein contained, the parties hereto hereby agree as follows:

     SECTION 1. Defined Terms. Unless otherwise defined herein, the terms used
                -------------
herein shall have the meanings assigned to such terms in, or incorporated by
reference into, the Agreement. For all purposes of this Amendment, "Effective
                                                                    ---------
Date" shall mean March 30, 2001.
----

     SECTION 2. Amendments to Agreement. The Agreement is hereby amended,
                -----------------------
effective on the Effective Date, as follows:

     (a) Annex A to the Agreement shall be deleted in its entirety and shall be
replaced with Annex A attached hereto, which Annex A shall be incorporated
herein.

                                       1
<PAGE>

     SECTION 3. Execution in Counterparts. This Amendment may be executed in any
                -------------------------
number of counterparts and by different parties hereto on separate counterparts,
each of which counterparts, when so executed and delivered, shall be deemed to
be an original and all of which counterparts, taken together, shall constitute
but one and the same Amendment.

     SECTION 4. Consents; Binding Effect. The execution and delivery by the
                ------------------------
parties hereto of this Amendment shall constitute the written consent of each of
them to this Amendment. This Amendment shall be binding upon, and inure to the
benefit of, the parties hereto and their respective successors and assigns.

     SECTION 5. Governing Law. This Amendment shall be governed by, and
                -------------
construed in accordance with, the laws of the State of New York.

     SECTION 6. Severability of Provisions. Any provision of this Amendment
                --------------------------
which is prohibited or unenforceable in any jurisdiction shall, as to such
jurisdiction, be ineffective to the extent of such prohibition or
unenforceability without invalidating the remaining provisions hereof or
affecting the validity or enforceability of such provision in any
other jurisdiction.

     SECTION 7. Captions. The captions in this Amendment are for convenience of
                --------
reference only and shall not define or limit any of the terms or provisions
hereof.

     SECTION 8. Agreement to Remain in Full Force and Effect. Except as amended
                --------------------------------------------
hereby, the Agreement shall remain in full force and effect and is hereby
ratified, adopted and confirmed in all respects. This Amendment shall be deemed
to be an amendment to the Agreement. All references in the Agreement to "this
Agreement", "hereunder", "hereof", "herein", or words of like import, and all
references to the Agreement in any other agreement or document shall hereafter
be deemed to refer to the Agreement as amended hereby.

                                       2
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 1 to
the Sale and Servicing Agreement to be executed as of the date and year first
above written.

                          AMERICREDIT MANHATTAN TRUST,
                          as Borrower

                          By:_________________________
                             Name:
                             Title:

                          AMERICREDIT FUNDING CORP. V, as
                          Seller

                          By:_________________________
                             Name:
                             Title:

                          AMERICREDIT FINANCIAL SERVICES,
                          INC., as Servicer

                          By:_________________________
                             Name:
                             Title:

                          AMERICREDIT FINANCIAL SERVICES,
                          INC., as Primary Seller

                          By:_________________________
                             Name:
                             Title:

                          THE CHASE MANHATTAN BANK, not
                          in its individual capacity, but solely as
                          Backup Servicer

                          By:_________________________
                             Name:
                             Title:

                                       3
<PAGE>

                          THE CHASE MANHATTAN BANK, not
                          in its individual capacity, but solely as
                          Administrative Agent

                          By:_________________________
                             Name:
                             Title:

                                       4
<PAGE>

                                            Annex A
                                            -------

                            SCHEDULE OF DEFINITIONS
---------------------------------------------------
                                (See attached)

                                       5