Really am not real knowledgeable on your questions except I generally do mechanical then body and paint so I don't mess up my "pretty" car.
If you have not already discovered it, our spnsor, Ames Performance is one of the largest Pontiac parts houses in the world.......and they have a large, free catalog for your Grand Prix. Phone them or fill out the form on their site. My A-body catalog they sent me is over 336 pages. They also have assembly manuals, shop manuals, etc. for our Pontiacs.
https://secure.amesperf.com/