[SickVette]

OK to clean the plastic. If it will fit in your dishwasher then put it in there. You will not believe how nice the pieces come out. If it does not fit there are products made specifically to clean a plastic part to prep it for paint. You can buy that at a auto body supply shop. If you don't have one of them then you can use denatured alchol. You can get that at Home Depot or any hardware store. Do not use laqure thinner or acetone those will eat the plastic. It is good to wear latex gloves while you are prepping the plastic also.

Sandpaper comes in many different grits. 220 is the grit to use. You can get it at any hardware store also but if you do find a local auto body supply I would get it from them in a 6' roll. When it comes to grits the higher the number the finner the grit. Like if you wanted to remove alot of material you would use 80 or 150 grit but those will leave alot of deep scratches. If you wanted to make something very smooth and shiny you would use 1500 or 2000 grit.
Paint...are you going to use spray can? If so I would proably say krylon. There are also companies making paint in a spray can for plastic. Sorry I don't have alot of info on spray can pait because I do not use it. That is a personal thing nothing against spray cans.

I think it is kick ass if you want to the stuff yourself and I think you are going about it the right way. Ask alot of questions and do research before you tear your car apart. You won't go wrong that way. Good luck