Uh...no, it costs less than $300 to change the fluid-I paid $355 but that includes a whole 12 quart case of the fluid that I bought and I think I only used 4 or 5 quarts.
The pan comes with a gasket, its rubber so you don't make one with RTV. Your dealer is trying to take advantage of you because people get hung up on this "lifetime fill" mystique and the fluid is proprietary. Its no less serviceable than any other transmission and you don't need special tools. Vern Diesel has over 370,000 miles on his 8HP70 and about half of that is towing. He changes with Valvoline MaxLife every 100,000 miles. I did mine around 66,000 miles-I don't buy into fluids that don't need changed.
I will challenge any of you to break one of the trans pans with anything short of a sledge once you pull it off the truck, they're pretty tough. They have four magnets in them.
http://www.ramforumz.com/showthread.php?t=235182