replacing clutch

Hi!
Need help.
I have a bad clutch on my `01 elantra... master & slave cylinder were replaced few month ago...
Driving on 3rd sometimes makes clutch slip, after starting from traffic light...
What parts do I need to replace?
Can I do this without removing the engine/transmission? Or I need to remove engine with tranny, and then replace clutch?
Please help! =)

Thanx so much!
Serg.