shifter linkage leak

Hi,

I have a 340 4 speed dart... I have a leak on what my mechanic says is where the shifter linkage comes out of the tranny.... a very small seal I suspect, but I am asking what is involved with replacing it? He is unsure, and dont want to remove the whole tranny to figure it out if there is an easy fix... any ideas? I also had one on the reverse light switch/sensor... replaced it and eliminated leak, but the other has me stumped... any advice to get rid of this annoyance would be great... thanks, AD