The "blowing cold air for hours" is concerning, I had an issue with my furnace not lighting, but after three attempts it would shut off. Your unit should have a similar feature, which if it continued to run would lead me to believe it thought it had ignited.
One thing I do, to make sure the furnace is getting gas, is to turn the stove on and then start the furnace. If you see the stove flame drop dramatically you may not be getting enough gas to light your furnace.
Whatever you do while troubleshooting the problem, keep your trailer well ventalated and have someone with you.
