Clutch not disengaging...

[Kallikak]

Over the past few days, I noticed the clutch on the Nissan was feeling softer, gradually getting worse. It was disengaging further and further through the stroke. Yesterday, I get in to leave to school, start it, push in the clutch, and try to engage reverse...it won't go. The clutch isn't disengaging fully, which means I had to slam the shifter into reverse, accompanied by the sound of angry synchros, in order to position it so I could jump-start the Chevy. I went to try to move the Nissan this morning, slammed the thing in reverse, and the damn thing is moving even with the clutch to the floor. Shit...I essentially have no use of the clutch pedal. I'm not sure what is wrong; I'm thinking the clutch master cylinder or slave cylinder. I was thinking I was just low on fluid, but there is plenty of fluid in the reservior (albeit, nasty, old and possibly original fluid.) Anyone ever experience this who could confirm my suspicion?