I have a bit more understanding of your position now. Awful one. I don't know how your area is, as in, how many Chevy dealers you have, or how many independent "reputable" shops you have. One possible route to take in gathering information, is to tow the vehicle to another Chevy dealer and have them inspect the prior work. Or towing to another independent shop, for a similar review.
As a technician, we are supposed to test drive the vehicle after certain work has been done, such as brakes or suspension, in order to confirm the repair or verify that there are no other issues after. Did the dealer do this? Is this a common practise there? These are some questions to ask. The second and third evaluations will also help document your case/problem. The 2nd & 3rd evaluations of the vehicle should have detailed informartion on what their opinion of the issue is and to also include some sort of explanation or proof as to why they concluded to said problem.
I hope you are able to gather all the information needed to be able to proceed and take the best route possible.