Another option for your floor is to use one of the new deck resurfacer products that are on the market now. They lock in splinters, seal up small cracks and waterproof the surface. The stuff is basically a cross between thick paint and undercoating and leaves a nice level surface with a little bit of texture and runs about $30 a gallon.
I just used some of this on my deck at home and a picnic table and was pretty impressed with it. The next time I have to replace a trailer floor, I'm going to look at this pretty close...
One big catch though, I would do it now before you get oil, trans fluid or gas on the wood. After that happens, I am not sure about adhesion....