Very good to hear that you got to the bottom of the roller question! You should not feel dumb. You hired a person that should know what they are doing, and we should be able to rely on them for the basics and not have to check everything that they do.
So for the next challenge: do you investigate yourself, consider using same tech or find someone else to do the work?
The Lippert Schwintek documentation (assembly, trouble-shooting,...) and free training videos are useful and there also some YouTube videos (less time for quick overview of how the slide works versus Lippert video).
One quick check is take a few photos of the aluminum racks that are mounted on the side of slide and post them to get opinions on the damage. Generally, the most wear is near the ends, maybe the upper.
Lippert may only sell the parts in kits so if rack is significantly damaged, drive gears need to be changed. The shoe likely is part of kit and should be changed while drive assembly is off. Vee roller could be part of kit. If slide moves out the motors and controller are fine and would not be part of the same kit.
So what I am saying is that if the rack needs to be changed it really does not matter if the other mentioned parts are bad since the drive mechanism has to come out anyway. I doubt if any of the parts you mentioned can be changed without removing drive mechanism.