'''++John Spaid++'''
you will have to replace the clutch itself. Once the lining wears down it will slip until it will l no longer make contact. Replace the throwout bearing and pressure plate as well. That way you will most likely never have to split the tranny from the engine. The hydraulic system refers to the way your clutch gets activated. Basically it is a hydraulic system down to the clutch assembly. It does not have anything to do with the clutch slipping.