You could dry the outside and wipe it with grease/wax remover then slather on RTV but it might still leak. Could be the old connector has wear on the plastic body, weak retaining clips, or a crack. You may have the wrong o-ring on it, could have damaged the o-ring going in.....etc,etc
The correct way is always a time consuming PITA initially - but it usually fixes the problem. If it was my transmission I would drop the pan and replace that connector and o-ring with a brand new unit making sure the inside radius where the o-ring sits was very clean - before sticking the new piece back in. Then cross my fingers. A new connector will run you anywhere from 3 to 10 bucks online.
http://www.transmissionpartsusa.com/...rts_s/5750.htm
For what it's worth I had a similar issue with the shift rod seal on my TH-400. Pain in the damn ass to get under there again after dropping the pan trying to figure it out - but when all done the leak free garage floor was worth the frustration.