I feel you on dealership service departments... at least they seem to acknowledge you have a problem.
Best of luck getting your vehicle repaired. You can try contacting GM/Cadillac custom assistance but you will likely come to the same opinion of their "assistance" that you have come to love from your dealer. It's worth a shot though, give them a call.
Each time I had my V in the shop they always seemed to give me a DeVille. I guess it was still a Cadillac at least.