It also could just be the seal behind the torque converter or seal at the tail shaft or pan gasket. or a loose cooler line (you didn't say where it was coming from). If the tranny works good, it's as much work to fix the leak, as it is to open the other and still not know till you put it back in.

I would just fix the leaks on the one thats in. as long as it works good. You can get the gaskets and seals & filter for it. You would still need the same parts for to put the other in also.

Pat