If your tires are wearing evenly you have no need to waste any money on an alignment. The same holds true for your car or truck. If your trailer does need an alignment you can get it done at most Big Rig spring and alignment shops. The typical RV dealer won't have the right equipment. It's not like aligning a car, there are no adjustments. They bend the axles into place. Don't worry they do this all the time on big trucks and trailers. I had mine done last year and Found it was off quit a bit. There is a system available called Correct Track that is touted as an alignment system for trailers. It will only do part of the job. It will not allow adjustments for toe or camber which can be done at an alignment shop.
B.O.