If you go in for a $49.99 special ask specifically what they are going to do and how they are going to do it. Personally I want the pan dropped and cleaned out along with the magnet. A fluid exchange by a machine is the easy way of changing the fluid and does not accomplish that. In fact, depending on the pressure involved, it might just stir up any debris in the pan. If the word "reverse flush" is mentioned, run like a pair of cheap pantyhose.
Not sure what to say about the MPG display.