I have found transmission shops to be the biggest ripoff there is. I wouldn't let them touch my car unless I had to (i.e., unless the trans is already shot). If you want maintenance done on your trans., I would go to your trusted mechanic for it.
I had a fluid change done once at a trans shop that I trusted. They told me the trans was "getting tired". Sure enough, a few months later, the trans started acting up...I was amazed at their expertise at predicting problems, but I decided to drop the pan and change the filter again...and lo and behold! My GM car had a screen in it (like a Ford's) instead of a real filter. I guess they must make them special for the trans shops, along with a script ("yeah...she's gettin' tired..."). I put a proper filter in and changed the fluid and never had another problem with that trans.