believe it's about 9 quarts or more. It's a shit ton of fluid.
If you really wanna be tedious and thorough, i'd flush the trans first (do a search for the poormans way of doing it) then change the filter/fluid. That'd end up costing you a little more but it may be worth it with your problem. Sounds to me like you just didn't have enough fluid to begin with and the pump is having to build up quite a bit of pressure to apply the gear.
God, I don't miss having an ATX.
Good luck,
joseph
FranklinDSM -- RIP (damn pole) The new car: '97 Eclipse GS