replace the clutch cylinder and slave. be done with it.
usually if one is going the other is not far behind. it is hard to tell which one is failing.
or bleed the thing, check the fluid. then replace.
it is just like bleeding the brakes..
or as I like to do, go to the local vets office get a 60cc syringe. over fill the rez. crawl under the truck. put a good finger full of grease around the bleed screw. loosen and pull 60 cc of fluid through it.
if there is fluid all over it,, replace.
I bleed my own brakes this way every time I take them apart.
the syringe is like a 1.25 and a bit of vacume tube.
don't bother saveing it. the fluid kills the syringe.