i would never take mine anywhere for service again. my last transmission went out 2 months after taking it to get flushed (4R100 w/ 60k).
if you do get a flush, do yourself a favor and go to the dealer. hopefully someone there will know what they're doing...maybe.
i would suggest dropping the pan yourself and just replacing the filter & fluid. when you replace the pan, get an upgraded B&M pan if you got the money with a drain plug. just my 2 cents
edit: oh...and those prices sound roughly bout right. dealer's probably closer to 200...