Re: Painting Fiberglass Bus
I'm no expert on painting but I wouldn't think you'd want to paint over the vinyl stripes. How much prep you do prior to painting depends on how picky you are about the final product but at least you want to sand off the gloss on the original paint. If the paint stripes have raised edges and they're not sanded flush they will show through the new paint. Ideally, you want a nice, flat, dull surface to paint over.
Fiberglass isn't that hard to repair, particularly if you're going to paint it afterward. Basicly you scrape out all the loose fiberglass from the crack, sand the edges with 80 grit sandpaper back to solid fiberglass, then fill the crack with Bondo-glass fiberglass filler. Once the filler dries sand it flat with 150 grit paper then prime and paint.
In general, it's best to prime first.