Wow man Im sorry to hear about your cars. I deal with a lot of high end cars, and only accept 5-10 cars a year. All I have is a small 16x32 steel building on the back of my dad's land. I have pretty much everything I need at my disposal there, having worked in corporate shops for many many years first. And in those years I have seen many many panels and whatnot broken, and ppl try to cover it up. Heck in the 06 Z06 that I did a month or so ago, I broke a panel, it was my fault, plane and simple, so what did I do, as soon as the owner of the vehicle came over to check out the progress(about 1am, only had 2 days to do the install), I told him. Told him I could have another panel tommorrow, since my brother is the manager at a GM dealer body shop. People come to me by word of mouth, and then I choose what cars I do and what I dont want to do, I suggest to some of my friends shop in the area. Basically all Im saying is, in a round about way, is just do alot of research before you take your car to a shop. And for shop owners/managers be honest, you have insurance, use it, everyone can make a mistake sometimes. At one of my shops the policy was, the first time you break something, they pay for it, after that its on you, you do it repeatedly, and you are getting the axe homie.
I hope everything works out for you and the GTO owner. Goodluck.