You'd have to look under the back of the truck and see what you've got for wiring. You'll need to verify whether the old owner tied into the old 7 way wiring or if they went the old school way and just tied into each tail light. Once you figure that out it should be simple. I'd assume all the wires are still back there somewhere, you just need to locate them.
As far as hooking anything to the battery. No, you won't have to do anything special, all the wires you need are at the plug under the dash.
Oh and, awesome looking retro camper, I love it! Does it have trailer brakes and you have just been towing all this time while not using them?