Need some help on my 1995 Damon Hornet 27T

Hi all, I just picked up a very nice looking 1995 Damon Hornet for a steal. Inside looks pristine. I've had to replace some burnt bulbs so far (1076 bulbs are hard to find) but it's too cold to do too much to the trailer. I have a couple questions that Google hasn't helped with. First, previous owner had no keys. How can I re-key the door lock and deadbolt? Second, I cannot get the Atwood LP furnace to start. The thermostat had a blown fuse so I replaced it and now the air unit in the roof comes on, but the furnace still does not start. The existing thermostat is a Coleman, but not a Coleman Maxx. Last question, I promise.. If I remove the dead battery from the unit and plug it in, will the missing battery have any effect on the rest of the systems? Thanks for helping me out on my first TT.