WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: View Of Headlining Trim Finish Molding
Courtesy of GENERAL MOTORS CORP.
Align the rear headliner trim finish molding to the retainer in the roof.
Press up on the rear headliner trim finish molding in order to engage the retaining tabs and clips.