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: Identifying Sunroof Opening Trim Bezel
Courtesy of GENERAL MOTORS CORP.
Pull inward on the sunroof opening trim bezel to release the tabs from the sunroof opening.
Remove the sunroof opening trim bezel from the headliner.