I drove my 2002 ranger 25 to 50 miles with almost no transmission fluid.. how bad is this going to be?

something must have started leaking really bad while i was driving. i noticed the truck starting to rev up like it had a slipping clutch even though it's an automatic. I limped it home only to find that it was about 2.5 quarts low on transmission fluid. (apparently it holds a total of about 3 quarts) It doesn't leak when parked but it must pour out pretty well when i'm driving. The only drip marks i've found anywhere was the one track of them from when i pulled into the driveway this last time so the entire problem only spans the last 50 miles i've driven.

I'm taking it to a good transmission shop on Monday but i'm really worried about how much damage there might be. I'm looking for thoughts on what part might be leaking only when driving as well as any educated guesses on what sort of damage the transmission sustained after the fluid dumped out.

the truck is only at 100k miles but has a few other problems. if this is leading to me needing a new transmission i'll probably have to consider getting rid of it.. money is pretty tight right now.