Your legal standing would appear to hinge on whether or not you received a written estimate for this size repair bill, and first approved them to do the work.

I'm not certain, but it's quite possible that NYS law requires this; even if not, I'd be surprised if MB allowed their dealers to operate without providing written estimates before proceding with repair work. It's simply good business practice.

If this is Romano outside Syracuse, I've had mixed experiences in dealing with them.