the clutch is hydraulic. I'm assuming the pedal is all the way to the floor and wont come up on its own correct?
you must have lost fluid somewhere, or gotten air in your system. check the clutch master cylinder fluid level(inside engine compartment on firewall at the drivers side, just to the right of the brake master cylinder). From there you can trace the small pipes to the dampener on the other side of the firewall and from there to the other connectors/fittings until you finally get to the clutch slave cylinder which is on the bottom of the transmission.
check for leaks all along these points and tighten up the connectors if needed. if it is leaking from the master cylinder itself you can either buy a new one from nissan, or pull the old one out and get a refurbishment kit. if it is the slave cylinder it is easiest to get a new one.
once you have fixed any leaks or replaced leaking parts, fill with DOT4 brake fluid and bleed the system to get the air out, making sure the fluid does not go below the min level.
it should work after that. it may take a few times of bleeding it.