Welcome. Try the cheap easy ones first. Scan for CELs even if the light is not on. Check ATF level, check condition (should be clear pink/red); buy a quart to compare. Might want to try the TSS and MLPS. The ATF is $30, TSS is $25 and MLPS is $50. All with how tos on this site.

Edit. ATF change
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=tranny&Number=992476&page=0&view=collapsed&sb=5&o=7&fpart=all&vc=1

Turbine Shaft Speed sensor.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=tranny&Number=257675&fpart=1&PHPSESSID=

Manual Level Position Sensor
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=trouble&Number=1040336&page=&view=&sb=5&o=&fpart=all&vc=1

"Always do the cheap and easy ones first." 1996 V6 ATX 96K miles