Removal Procedure

WARNING: This page is about a different car, the 2002 Cadillac Seville. However, it is still accessible from the selected car via links, so may be relevant.

Remove rear shelf trim panel. Refer to TRIM PANEL REPLACEMENT - REAR WINDOW SHELF .
Disconnect the GPS antenna wire harness from the retaining clips on the rear shelf trim panel.
Remove the pushpins (1) retaining the GPS antenna module (2) to the rear shelf trim panel by pulling out on the center of pushpin and then pulling out the entire pushpin assembly.
Remove the GPS antenna module (2) assembly from the rear shelf trim panel.

Fig 1: Removing Pushpins & GPS Antenna Module
Courtesy of GENERAL MOTORS CORP.