a lot of us have small drips--if mine, with drips, stay full, I don't worry about it. When I start leaving puddles as opposed to spots, I will fix my problems. Maybe even the trucks problems too. (ha ha). It is probably the input seal to the transmission. It is kind of a pain to fix, because of its position--more of a labor than part issue. It would probably take me several hours, so I imagine it is probably a few hundred bucks in labor to have fixed. The seal is not expensive. just a pain to get to. I have a drip from the 0-ring between my transfer box and transmission. Been dripping about 8 months. I opened up the transfer box and it was nearly full. Good enough for me to leave it alone.
What you will want to make sure of, though, is that it does not get on the clutch--not only will it slip, but that will pretty much be it for the disc. You would need an awful lot of fluid leaking for that to happen--I think you would know it if you were in trouble. That being said, I would probably wait until I replaced my clutch until I dealt with that problem. Usually they just drip a little.