First off, welcome to the board!
If you have nitro on the neck, you can just add to it. If that isn't working out for whatever reason (color, finish quality, etc.), it's very easy to strip. Lacquer thinner will take off the existing finish pretty quick.
The body is a different story. Warmoth shoots poly on their bodies, which is difficult to strip or paint over. But, it can be done. If you're going to shoot nitro over it, then you need a barrier coat of shellac, after which you can shoot pretty much anything you want on there. If you want to strip it and start over, you need a powerful stripper that isn't available everywhere. But, just check the ingredients. If it has methylene chloride in it, it'll work. It's wicked stuff, though. Be careful with it, and follow all the precautions The stuff really can hurt you.
Of course, you could also just sand the body clean, but you need to be part masochist to take that on. Lotta work, lotta time.