I can feel your pain about the pending dealer trip, but that is probably the best solution. As one of the greatest fears is having the truck scratched/marked when they remove a door panel or something.
Grab your camera, take some pix of the door area and the hood/fender area prior to service. Explain your concerns to the SM, and ask him to verify that the photos are a true representation of the condition of the areas in question....heck, even take the photos with him standing right there. If he cares at all about you and your vehicle, he shouldn't be offended at all, but rather encouraging of the said act. Just make sure you approach this in a way that you would be happy with if the roles were reversed. Any hint of accusation or real distrust will likely put him/them on the defense, and that would just lead to a negative experience for all.
Just my .02......my SM liked my idea so much, he even went and got his camera. I have a great dealer!