HI Mike, I installed the aftermarket Correct Track system on our 2008. The system only allows you to move axle mounting points front-to-rear in 1/4" increments. The alignment on a trailer is simple, the axles must be parallel to each other and also square to the trailer.
Loading does not affect anything you can adjust with the Correct Track. Loading WILL affect the camber, but the camber is built in to the upward curve of the axle when it's made. If you lose camber due to overloading, you must replace the axle, there is no adjustment for it.
If you don't have an indication that alignment is off as evidenced by uneven tire wear, then I would not pay the dealer to do any alignment.