the mk2 is supposed to run dexron II atf which is red, says so on the reservoir. though there is no telling what the old stuff is. Its thicker than the green stuff so if anything green fluid will cause leaks.
If you let the level get too low the pump starts to get air in and ends up blowing the fluid out of the tank, I've been there!
I wouldnt get a new pump just yet though, look over the entire system to make sure there arnt any other leaks you didint know about, if it looks good try it with new fluid and give it a bleed (turn from lock to lock, make sure to keep fluid to max at all times)