i agree with young blood im 18 and already inhaled the fumes while painting always wear your mask. But i can answer your questions. On the sanding or bare metal i'd say where its peeling sand to metal and feather the rest out i'd say just to be on a safe side use 320 grit, mask it off, then get some 3900s (first kleen) wet a rag and go all over the hatch and wipe off with a dry rag, now spray a self-etching primer and then three-four coats either lacquer primer or uro primer. I prefer lacquer do to easier wet-sanding. on the trim pieces are you wanting to reuse them or get new ones?