3.3 and 3.8 V6's, MUST READ FOR ALL!
Another option (if you don't feel you're getting anywhere with a particular dealer) is to bump it up the food chain. There will be a regional manufacturers representative that oversees all the franchises for a state or several states.
They don't have to defend the original diagnosis, but are supposed to keep customers happy. Don't start there, or they'll just send you back, but if you think you've taken all reasonable steps with the dealer and aren't getting satisfaction, it's an option.
My sister-in-law was having problems with a local Ford dealer (I know, I know...no snide jokes about that's the problem) and wound up with the West Coast Sales Manager telling the dealer to give her a new car to replace the one they couldn't seem to fix the transmission on.
I call it the Plumbing Rule of Bureaucracy - S**t rolls downhill!
Jay