<PAGE>   1
                                                                    EXHIBIT 4.28




                          CERTIFICATE OF INCORPORATION

                                       OF

                            CLASSIC OF OKLAHOMA, INC.


         THE UNDERSIGNED, acting as the incorporator of a corporation under and
in accordance with the General Corporation Law of the State of Delaware, hereby
adopts the following Certificate of Incorporation for such corporation:

         1. Name. The name of the corporation is Classic of Oklahoma, Inc. (the
"Corporation").

         2. Duration. The Corporation is to have perpetual existence.

         3. Purpose. The Purpose for which the Corporation is organized is to
engage in any and all lawful acts and activities for which corporations may be
organized under the General Corporation Law of the State of Delaware.

         4. Authorized Shares. The aggregate number of shares that the
Corporation shall have authority to issue is 1,000 with the par value of $.01
per share. All of such shares shall be designated "Common Stock."

         5 Registered Office, Agent. The registered office of the Corporation is
to be located at 9 East Loockerman, Dover, County of Kent, Delaware. The name of
its registered agent at such address is Capitol Services, Inc.

         6. Incorporator. The name and address of the incorporator is as
follows:

                                Timothy E. Young
                         Winstead Sechrest & Minick P.C.
                         100 Congress Avenue, Suite 800
                               Austin, Texas 78701

         7. Initial Directors. The powers of the incorporator shall terminate
upon the filing of this certificate and the following persons shall serve as the
directors of the Corporation until their successors are duly elected and
qualified:

                               J. Merritt Belisle
                         515 Congress Avenue, Ste. 2626
                               Austin, Texas 78701

                                 Steven E. Seach
                         515 Congress Avenue, Ste. 2626
                               Austin, Texas 78701


<PAGE>   2







         8. Arrangement with Creditors. The following provisions are included
for the management of the business and for the conduct of the affairs of the
Corporation, and for further definition, limitation and regulation of the powers
of the Corporation and of its directors and stockholders:

                  (a) The Board of Directors of the Corporation shall have the
         power, without the assent or vote of the stockholders, to adopt, amend
         or repeal the Bylaws of the Corporation in such manner and subject to
         such limitations, if any, as shall be set forth in the Bylaws.

                  (b) Whenever a compromise or arrangement is proposed between
         this Corporation and its creditors or any class of them and/or between
         this Corporation and its stockholders or any class of them, any court
         of equitable jurisdiction within the State of Delaware may, on the
         application in a summary way of this Corporation or of any creditor or
         stockholder thereof or on the application of any receiver or receivers
         appointed for this Corporation under the provisions of section 291 of
         Title 8 of the Delaware Code or on the application of trustees in
         dissolution or of any receiver or receivers appointed for this
         Corporation under the provisions of section 279 of Title 8 of the
         Delaware Code, order a meeting of the creditors or class of creditors,
         and/or of the stockholders or class of stockholders of this
         Corporation, as the case may be, to be summoned in such manner as the
         said court directs. If a majority in number representing three-fourths
         in value of the creditors or class of creditors, and/or of the
         stockholders or class of stockholders of this Corporation, as the case
         may be, agree to any reorganization of this Corporation as a
         consequence of such compromise or arrangement, the said compromise or
         arrangement and the said reorganization shall, if sanctioned by the
         court to which the said application has been made, be binding on all
         the creditors or class of creditors, and/or on all the stockholders or
         class of stockholders, of this Corporation, as the case may be, and
         also on this Corporation.

         9. Director Liability. To the fullest extent permitted by the General
Corporation Law of the State of Delaware, as the same exists or may hereafter be
amended, a director of the Corporation shall not be liable to the Corporation or
its stockholders for monetary damages for breach of fiduciary duty as a
director.

         10. Indemnification. The Corporation shall indemnify any person who was
or is a party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (whether or not by or in the right of the Corporation) by reason
of the fact that he is or was a director, officer, employee, or agent of another
corporation, partnership, joint venture, trust or other enterprise, against
expenses (including attorneys' fees), liability, loss, judgments, fines and
amounts paid in settlement actually and reasonably incurred by him in connection
with such action, suit or proceeding to the fullest extent permitted by either
(i) any applicable law in effect on the date of incorporation of the
Corporation, or (ii) any law which becomes effective during the existence of the
Corporation and which is applicable to it.

         11. Bylaws. In furtherance of and not in limitation of the powers
conferred by statute, the Board of Directors is expressly authorized to make,
alter or repeal the Bylaws of the Corporation.


<PAGE>   3


         12. Election of Directors. Elections of directors need not be by
written ballot unless the Bylaws of the Corporation shall so provide.

         I, THE UNDERSIGNED, being the incorporator hereinbefore named, for the
purpose of forming a corporation pursuant to the General Corporation Law of the
State of Delaware, hereby declaring and certifying that the facts herein stated
are true, and accordingly have hereunto set my hand effective the 2nd day of
February, 2000.


                                             /s/ TIMOTHY E. YOUNG
                                             -----------------------------------
                                             Timothy E. Young