This Theta (my 2nd V and 4th Theta overall) came to me already disassembled, roughly 
I bought it “as-is” on eBay for cheap, with a scratched lens and a missing battery. It looks like somebody scratched the lens then pried the case apart with a big screwdriver to harvest the battery before selling. I added the battery then carefully reassembled, and it works great now, no excessive heat nor any other issues 
I think disassembly would be easy, remove the bottom sticker, take out the 4 little screws, then pry apart the case.
Those are the batteries, yes.