Two major locations of leaks (besides the pump) are at the control valve and the ram. Both are rebuildable, however extreme caution has to used while removing the control valve. Do not use a pickle fork on the stud, it will tear apart the sleeve inside and complicate things immensely.
If you have the cash you can buy a new control valve, the ram on the other hand isn't too expensive. Find out exactly where the leak is coming from before you do anything though - could just be an old hose.