After seeing a dealer installed tube bumper accessory on an 86 CJ7 almost fall off while pulling a small utility trailer I dont trust anyone but myself. I cut the holes in my bed for the picture frame puck pockets and installed a Super glide on my truck. Obviously everyone isn't set up to do this type of work.
I dont think I would go to a U haul type place as I would consider them more of a trailer hitch place. I'd look for a dealer selling a lot of FW. It wouldn't hurt to look it over yourself when they are done. From there on keep an eye on it to see if anything loosens up or it starts making unusual noises or any glitches develop.