just like it says. is there a way to know which one it is that has failed? i don't have leaks anywhere. and have bled the lines. TIA

You can't tell unless you take off the cylinders. If either fails, then (typically) you have the same result: your grab point for the clutch moves down into the floor of the car, to the point where it won't disengage.

I'd merely look for leaking at the location of each one. Hence, look down by your clutch pedal, for the shaft of the master cylinder, and look for fluid. Then get under the car, to the location of the slave cylinder, pull back that rubber boot, and see if there's any fluid there. If you see any fluid, at either location, it's leaking and needs to be replaced or rebuilt.

if you keep pushing the pedal down with a bad slave cylinder (first one to go) you risk throwing the seal in the master. there is no way to tell...unless of course, you replace the slave and it's fixed. or replace both. if replacing both start by bench bleeding the master and working your way down.

how much would it cost for both brand new slave, master and the line?

i dont know about the master or the line....
but my slave went out and had it towed to satan for lack of access to a shop (big mistake) and paid somewhere around 250 just for the slave (and install and bled the system.... blah blah)

x(

there's not many place for that brake fluid to go. For Slave it'd leak at the slave cylinder. For the master it may leak at the master or it maybe leaking through the seal on the firewall and dribble down you clutch pedal. Bleh found out that's where the leak is on my Z.

if the seals of the master cylinder are bad or the rubber inside the master cylinder is bad then you can just simply rebuild it for less than 20 bucks. Go to your local parts store they'll have a master cylinder rebuild kit. Raybesto (sp?) makes it.