i need a good adhesive to put my roof supports back up from the snow. It looks like the factory used almost a cushion adhesive and the supports for the roof are not directly on the sheet metal.

Polyurethane adhesive. Probably the heated kind was used for that application. Something you cant get off the shelf or have the equipment to apply. A auto paint/body supply house would have the next best thing, a little better than but of the same material as Liquid Nails. It doesn't set well in the cold.

what can i use to hold that peice of plastic molding in between the front wheel iand the front door in place its coming off at the top and it looks like its held on by two sided tape.

I've had really good luck with the 3M Moulding Tape for various automotive projects over the years Shop 3M: Scotch-Mount Molding Tape. You really need to make certain that the mounting piece and the bonding area are free and clear of wax, grime and grease. Use a strong solvent first then just prior to using the tape, wipe all tape contact surfaces down with rubbing alcohol, and then wipe dry again. You can get the tape at most automotive part'* stores. Use the widest tape you can for maximum bonding surface area.

Yep, it is double faced tape and GM has alot of troubles with it. The 3M stuff is far superior to OEM. I had several places popping up out of place.