Actually $90 isn't too bad. Shops around here start at over $100 for a full automatic transmission flush. A couple of mechanics I talked to said that a conventional transmission fluid change only changes about 60% of the fluid. The only way to change it all was to drop the transmission! Now some shops have a device which they claim will flush out all of the old fluid without having to drop the transmission. I haven't tried that yet but if that's what they're going to do for you, let us know how you make out!