It is always good to put your information in your signature. We had no indication that it was an ATX until your recent post. You may want to check if the ATF level is correct and the color is clear pink/red (buy a quart of ATF and compare). If the ATF color is close, you may want to try changing it first. If they mean changing the filter screen for $70, that is a steal but I doubt it. They are probably just going to do a ATF drain and refill once.
Edit. ATF change how-to
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=tranny&Number=992476&page=0&view=collapsed&sb=5&o=7&fpart=1
