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: Identifying Engine Manifold Cover
Courtesy of GENERAL MOTORS CORP.
Remove the engine oil fill cap.
Remove the oil fill pipe.
Pull up on the cover in order to disengage the cover from the studs.