IMO, the deep pan is a band aid for a bad seal on the trans. Fix it right the first time. You can do this seal replacement without pulling the valve body, dropping the pan and if the trans is clean you won't even get your hands dirty (much).

Take the kickdown and selector lever off the trans (both pinch bolts) and take a sharp pick to work the selector shaft seal out of it's hole and up the shaft. It's a press fit, so jab the pick through the top of the old seal and use leverage.

Take the new seal, lube it a little and slide it over the shaft until it sits evenly on the trans case, not cocked. Take a deep socket the same size as the seal and slide it over the shaft to rest on top of the seal. Tap the socket until the top of the seal is flush with the trans case. Re-install selector/kickdown levers.

I have done many this way. The worst I have had to do is un-bolt the trans crossmember to drop the end of the trans down for a little more room to work.

Jeff