Oooof i feel for those O/Os when my rig was down after my wreck it was rough. Trying to replace one with things how they are is going to be a nightmare.
As towards the fire any bets that it was either one of those little aux heater dodads or someone who was running a 120 volt whatever off his 12 volt system and overheated the wires? I know the one time i tried to charge my laptop off a 120 volt adapter it melted my cig lighter.