Many trailers (most) have a circuit breaker or fuse close to the battery near the tongue. Sometimes, they're tucked down near the frame. Check to make sure that circuit breaker isn't tripped, there may be a reset button on it (tiny).
You really need to get a multimeter, especially when going off-grid. You will be your own power plant so you will need to know where, when, how much electricity is going to what, when, how, and how much. Cheap multimeters can be had at Harbor Freight, Sears, Home Depot, etc.
When we know that you have power at a certain point, we can diagnose and help you get going. It's not difficult. If I was going completely off=grid, I'd have solar working for me immediately. The price and logistics of getting gas into the generator and the noise would be the two things I can live without. I have a single 235W module that takes care of all my power needs. I run a small dorm fridge, a 32" LCD screen, stereo, and all the other 12V stuff with the solar. My furnace doesn't use 12V but I bet yours does and the draw of the furnace will be significant. This is where additional batteries come into play. LED light bulbs at $2/bulb will save you a lot of juice, too.
First, get that meter and post back where you have 12V and we'll guide you through.
