Hi Sean,
first off if you have 110V I would get to Walmart, Target, etc and get a space heater to help out until you get the furnace figured out.
Based on your earlier posts I don't think the battery, or lack of battery is the issue. But you can eliminate that pretty quickly with your vehicle and a pair of jumper cables. Just make sure you observe polarity on the battery wires as trailers many times use white wires for ground. So hand trace the battery wires back until you find the one that goes to a bolt on the frame. This will be the negative cable (-) Also disconnect from shore power before hooking up the jumper cables so you don't feed any power from the converter to your vehicle.
Is your thermostat an AC/Heat combination stat or is it heat only. If it's heat only try taking it off the wall. If there are only two wires then disconnect one wire and touch it to the other wire. If your thermostat is bad then this will turn on the heater.
As far as finding the heater is the underbelly covered or can you trace the floor vents back to the heater by looking under the trailer?
Here's a different type of furnace vent posted by ever1ast15
linkThe vents are built into the furnace so if you find the vent you have found the end of the furnace.