You have to face it, every business owner eventually finds a customer that they cannot satisfy. Without placing blame, that is where they see you now.
They already replaced your transmission, you've been "in upteen times over the last 18 months to have every little noise checked out", you have very high mileage and now your engine is worn out.
You are not their favorite customer, they already lost money on you, and you are already lost as a future customer. So they only really have two worries when they snub you, the lemon law and bad word of mouth. Obviously, your post starts the bad word of mouth.
This where the lemon law starts:
http://www.nh.gov/safety/divisions/d...law/index.html