I hope you've got another dealer nearby. I don't think I would trust those guys.
Remind them of the magnuson moss act. They cannot void warranty for doing your own maintenance unless they can prove that your work IS the cause of the failure.
Tightening bolts and clamps doesn't take a Rocket scientist (well ok, maybe in this case it does); if you're pretty sure you can do it without stripping or breaking them, why waste the time waiting on the dealer?
Scott