Ok from what I know about body work and paint here is a bit of info I can give you that I know for sure.... if the paint on the bed now isn't in really bad shape then sand the whole thing down with 280-320 grit with a flat board (line board, whatever you wanna call them) and then a plain little hand block and scruff up all the old paint through the clear coat.... After that, prime it and paint it. If the old paint on the bed now is pretty bad or there are more than just one layer of original paint then sand down to bare metal. Start with 40 grit or such and then go to 80, then about 150-180, etc. All depends though, some people say to use 150, some say 180, everyone has their own oppinion here.