If the level is low and it has sat that long the slave and the master are wasted. save your self the time and trouble and change them out as a pair. use new dot 3 brake fluid. check the line. then bleed the system. have a freind pump the clucth pedel 10 time then on the tenth one hold it to the floor and you can open the bleed valve on the slave to let the air out. then close the valve and your freind can release the pedel. repeat several more times, then see how it feels. change all the fluids in the car while your at it. coolant , brake , diff, trans.
Oils cheap, engines are not.
Write me if you need more info. Im a ASE Master tech and work for Toyota.