The very first thing I would do, is invest in a tool that tells what you have in the first place. I forget the name of this tool, but it looks like an air pressure stick gauge, and works with a magnet. You stick the tool to the body in a few thousand places, and pull it off, and read it....
If the reading are uniform, maybe you can get away with less work..... maybe you will find a ton of patch work, and will have to work hard getting the old finish off.... Mac