Well, to remove old paint, I used to get those big ziplock freezer bags, place the component inside and spray EZ Off oven cleaner (wife uses fume-free, so that's what I used). Seal the bag overnight and let it soak. The paint would mostly come off and I'd use a toothpick (many) and an old M-16 cleaning kit toothbrush (any old brush would do).
After the paint was mostly gone, I'd try to pry apart the pieces, sometimes putting the kit in the freezer overnight to make the glue joint brittle and easier to pop apart. Sand and prep parts for reassembly, etc. I was surprised how many kits I built that I did not remove mold seams or even sprue burrs back in the day.
Of course after getting into a discussion with someone on RMS regarding paint stripping, this old retired Air Force NCO sent me a sample of his new Strip-A-Kit product and asked me to try it. It works well, better than the oven cleaner, but the zip lock bags and oven cleaner were normally readily available in many households and the S-A-K is relatively new and can't be shipped overseas. If you see it on the shelf, grab some and give it a whirl.
Anyway DJ, if you want to just re-do the kit. Strip it, clean it up, reassemble and repaint. If you want to improve it, you can add photo etch, aluminum gun barrel, aftermarket decals, but then sometimes it is cheaper to buy the latest kit than it is to update an old kit. Unless the kit has sentimental value (kind of like my old M113A1).