Hey Mike,
It's fairly easy to replace those but you need the Mb software to transfer all the data over. Those ETC modules are pretty pricey, the quote sounds about right.
As far as not trusting the dealership 100% I understand. But Dave Holt has a new tech who came from Portand (where I am) who is a master guilde and a really nice guy. He's likely to be one of the best in Oregon if you ask me. His name is Aaron and he can be trusted......that's if you take advise from random people on-line. Good luck.