for your main question above, i looked through the workshop manual and there is no definitive answer, it states if you do any internal work to the transmission then you should hook it up to a scan tool to perform a calibration proceedure, however the vehicle should drive without the calibration,
on the electrohydraulic unit (valve body, i think they are the same thing), sticking or clogged valves and soleniods is a common occurrence, (open transmission and clean) condition of the tranny fluid could help diagnose,
have you tried disconnecting the Ground cable for 10 minutes then reconnect this will reset the vehicles computers and put the transmission into self calibrating mode, worth a try it's free and can't do any harm,
have you checked the fluid level, too much or too little fluid causes shifting issues,
clogged filter in the tranny,
is there any fault codes set,