I would double check all of the battery connections, and compare them to the notes/pictures you took before you disconnected anything. You did take notes, didn't you?
Since you say things stopped working as soon as you changed out the batteries, I strongly suspect that you didn't hook something up properly.
Adam and Sue, and a pack of little furballs
2007 Holiday Rambler Endeavor 40PDQ Limited Edition - Cummins ISL 400
2013 Ford F-150 FX4 toad - USGear Unified Tow Brake, Roadmaster Blackhawk II Tow bar, Blue Ox baseplate
Home base near Buffalo NY, often on the road to a dog show