Hey there,
Though there are a lot of folks on this forum that are far more expert than me on this subject, I figured I'd at least throw out some thoughts for you.
Refinishing a bass seems pretty daunting but if you take your time and do it right, it's surprisingly manageable. The "taking your time and doing it right" part, though, is where the focus lies.
First off, check out the reranch forums, every sort of expertise as far as finishing is concerned, is represented there;
The Guitar Refinishing and Restoration Forum :: Index
Now, the first thing to consider is taking the bass apart; this isn't very difficult as long as you're careful and patient; un string the instrument, then slowly and carefully remove the screws on the Neck, Bridge, Pickguard, and Straplocks. Make sure you have a properly sized screwdriver (you'll probably need at least 3 different sizes for the whole bass) otherwise you'll strip out screw heads and have an awful time in the future trying to ever work with them again (trust me, I know!)
Now to take the original finish off of the body, there are a few ways which you'll have to research and decide for yourself. You can use chemicals to break down the paint, like Citrus strippers, or some of the really harsh stuff that will require some safety gear, or you can use a heat gun and a scraper, or, the last and probably most painstaking option, is sanding.
Now, you'll have to do some sanding regardless of how you get the factory finish off, but if you try to sand it all the way off, be warned, it takes a long time and you run the risk of damaging the original roundovers and contours (once again, speaking from experience
)
Once you have your original paint off, you want to sand and smooth your wood to at least 220 grit sandpaper if not higher. I'm working on a stratocaster right now that I brought the wood up to 320 grit, but we had to do a lot of work to remove original gouges and dings from the first time it was refinished. Again, I reiterate; GO SLOWLY!
once you get the body down as naked as it can go, then you get to start doing the fun part; building the new finish! This is actually a much slower task than the stripping portion but it is a labor of love that will reward you greatly if you are patient. once your body is sanded, a coat of sanding sealer will even out the grain of the wood and close the end-grain bits in the side of the body. After that, a coat or two of sandable primer followed by a high-grit (I have been doing 400 grit with pretty nice success) sanding to level and smooth everything out.
Once you start on your colors, make sure to give plenty of time between coats/colors for the paint to fully cure, and don't be afraid to give it some high-grit wet sanding after coats have set up, to smooth them out (400-800 grit for this)
Once you've got your colors in place, the clear coat is the part that really makes the difference. There are many ways to do it and in my very amateur experience, the krylon spray acrylic works pretty well if you spray light and even coats, wait the full 24-48 hours to cure, then wet sand up to 2000 grit, and apply the next coat.
Done properly, it will look like it's been that way all it's life.
If you were thinking of just applying paint over the coat that's already on there, keep in mind it will never look as good or as "deep" as a factory finish. If it's what you really want, then go for it, it's your instrument, but do consider doing things the longer but better way.
Also, as far as the setup and the rotosounds go, setups for the fender (including squier) P Bass can be found at the Fender website under their support section. That should give you all of the pertinent numbers to go off of, while there are MANY threads on this very forum as well as all across the internet that describe how to accomplish all the tasks required in getting that perfect setup. It's a wonderful learning experience that every player should try and surprisingly easy once you do it once or twice and get a feel for it all.
Again, TAKE YOUR TIME, and DO IT RIGHT, and you'll have a killer axe.
