Silly GM, in their haste to please only made a few different arrangements on the rear tail lamp assemblies and as you did not specify as to bulb or lamp assembly. I am sending the most popular as the lamp needs to come out to access the bulb anyway. If this is not correct, please update me. The more info the better. Such as sedan or extended sedan. This is for the standard sedan. Thanks
Tail Lamp Assembly and /or Backup, Sidemarker, Stop, Turn Signal Bulb Replacement (Sedan) Removal Procedure
Tighten Tighten the tail lamp screw to 2 N·m (18 lb in).