WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: View Of Socket & Bulb
Courtesy of GENERAL MOTORS CORP.
Use a small flat-bladed tool to disengage the lamp lens. Remove the lens from the rearview mirror.