the insurance company is involved and all the paperwork no doubt is written to restore the car to its original likeness. Unfortunately if you did not specify with the insurance company the use of your aftermarket parts, they are not really covered. Thus if you get into it with the body shop, he can just go back to what is in the estimate from the insurance company. You should've got everything you talked to the guy about in writing. He has an out because everything else was verbal. So I would try my best to work it out with the guy without getting him annoyed. It sucks that you cant find good work these days.