Yorb wrote:. And how do i check my slave cylinder?
Visually inspect it. If there is signs of fluid from the rubber boot area, you should replace it, its about to bust. If it is clean and dry, look into bleeding it, you may have somehow gotten air trapped in the line.
As for your noise when the transmission is in gear, my first thought would be throw out bearing, since its only in use when the pedal is pushed in. Whoever replaced your clutch should have offered to replace that as well, just because its right there. And if you say you are leaking from the rear main seal, then thats something that you shouldve been advised to take care of while the transmission was off for the clutch job (its right behind the flywheel).