<PAGE>

                                                                 Exhibit 10.11-B
                                                                 ---------------

                      ASSIGNMENT AND ASSUMPTION AGREEMENT
                      -----------------------------------

     Assignment and Assumption Agreement (the "Agreement"), dated as of
December 21, 1997, between Nevwest Limited Partnership, a Delaware limited
partnership (the "Assignee"), and Raymond L. Gellein, Jr., Trustee of Raymond L.
Gellein, Jr. Revocable Trust (the "Assignor").

                                R E C I T A L S:
                                --------------- 

     WHEREAS, Assignor is the owner of 2,769,030 shares (the "Shares") of common
stock, $.01 par value per share, of Vistana, Inc., a Florida corporation (the
"Company");

     WHEREAS, Assignor is transferring a portion of the Shares to Nevgel, Inc.
("Nevgel") and the remainder of the Shares to Assignee and Nevgel is
transferring such portion of the Shares to Assignee.

     WHEREAS, Assignor and certain other shareholders of the Company have
provided for the voting and transfer of their shares of common stock of the
Company, including without limitation the Shares, pursuant to that certain
Shareholders' Agreement dated as of February 10, 1997 (the "Shareholders'
Agreement");

     WHEREAS, the Company has granted to Assignor certain registration rights
pursuant to that certain Registration Rights Agreement dated as of February 10,
1997 (the "Registration Rights Agreement"), among the Company, Assignor and the
other parties thereto;

     WHEREAS, Assignor has agreed to certain restrictions regarding the transfer
of the Shares pursuant to that certain letter dated December 4, 1997, from
Assignor to NationsBanc Montgomery Securities, Inc. ("NationsBanc") (such
letter, together with any other lock-up letters from Assignor to Nationsbanc,
the "Lock-Up Agreements");

     WHEREAS, Assignor has granted to certain employees and former employees of
the Company and its subsidiaries and affiliates options to acquire certain of
the Shares pursuant to those certain Shareholder Option Agreements described on
Schedule A, attached hereto and by this reference made a part hereof (the
"Option Agreements" and, together with the Shareholders' Agreement, the
Registration Rights Agreement and the Lock-Up Agreements, the "Agreements"); and

     WHEREAS, Assignor desires to assign to Assignee all of Assignor's rights
under the Agreements (other than the rights of Raymond L. Gellein, Jr. under
Section 3 of the Registration Rights Agreement) and Assignee desires to assume
the obligations of Assignor under the Agreements as provided herein.

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


<PAGE>
 
     1.   Assignment.  Assignor hereby assigns, transfers and conveys to
Assignee all of Assignor's right, title and interest in, to and under the
Agreements (other than the rights of Raymond L. Gellein, Jr. under Section 3 of
the Registration Rights Agreement).

     2.   Assumption by Assignee.  Assignee hereby assumes and agrees to
perform all of the obligations of Assignor under the Agreements.

     3.   Binding Effect.  This Agreement shall inure to the benefit of, and be
binding upon, the parties hereto and their respective successors and assigns.

     4.  Trustee Liability.  This Agreement, to the extent executed by any
person or entity in his or its capacity as trustee of a trust, is executed by
such person or entity solely as such trustee and not in an individual capacity.
The execution by such person or entity of this Agreement in his or its capacity
as trustee shall not create any liability on, or require the performance of any
covenant by, any such trustee individually nor subject the individual property
of such trustee to any liability.

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement on the
 date first written above.


                                            ASSIGNOR:

                                            /s/ Raymond L. Gellein, Jr.
                                            ------------------------------------
                                            Raymond L. Gellein, Jr., Trustee of 
                                            Raymond L. Gellein, Jr. Revocable 
                                            Trust

                                            ASSIGNEE:

                                            NEVWEST LIMITED PARTNERSHIP, a 
                                            Delaware limited partnership

                                            By:  Nevgel, Inc., a Nevada 
                                                 corporation, its general 
                                                 partner

                                                 By:  /s/ Gordon W. Stewart 
                                                      --------------------------
                                                      Its:  Secretary
                                                            --------------------


                                      -2-
<PAGE>
 
                                   SCHEDULE A

                         SHAREHOLDER OPTION AGREEMENTS


Shareholder Option Agreement dated as of February 10, 1997, among Assignor,
  Matthew E. Avril and the other parties thereto.

Shareholder Option Agreement dated as of February 10, 1997, among Assignor,
  Alain J.A. Grange and the other parties thereto.

Shareholder Option Agreement dated as of February 10, 1997, among Assignor,
  Barbara Hollkamp and the other parties thereto.

Shareholder Option Agreement dated as of February 10, 1997, among Assignor,
  Carol A. Lytle and the other parties thereto.

Shareholder Option Agreement dated as of February 10, 1997, among Assignor,
  James A. McKnight and the other parties thereto.

Shareholder Option Agreement dated as of February 10, 1997, among Assignor,
  William J. McLaughlin and the other parties thereto.

Shareholder Option Agreement dated as of February 10, 1997, among Assignor, 
  John M. Sabin and the other parties thereto.

Shareholder Option Agreement dated as of February 10, 1997, among Assignor,
  Susan B. Werth and the other parties thereto.

Shareholder Option Agreement dated as of November 18, 1997, among Assignor,
  Charles E. Harris and the other parties thereto.

Shareholder Option Agreement dated as of November 13, 1997, among Assignor,
  William J. McLaughlin and the other parties thereto.

Shareholder Option Agreement dated as of July 17, 1997, among Assignor, 
  Alain J.A. Grange and the other parties thereto.


                                      -3-