I tried just removing the baseplate, but like I said, everything is pretty well frozen up. There's a fair bit of corrosion. I don't know if it got wet at some point or if it was stored in a humid area, but don't think it will be possible to get it going again without opening it up a little more, if at all.
If the photo in your first post is of the camera you're working on, it looks as though water found it's way into the base of the body. Good luck.