WARNING: This page is about a different car, the 2002 Pontiac Montana, 2002 Oldsmobile Silhouette, and 2002 Chevrolet Venture. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Roof Auxiliary Air Outlets
Courtesy of GENERAL MOTORS CORP.
Use a small, flat-bladed tool in order to press in on the retainers on the roof auxiliary air outlets.
Pull the roof auxiliary air outlets from the headliner.