[s-cars] When clutch plate wears out, why does disengaging the clutch become difficult/stiff?

[Paul.Park at colorado.edu]

My clutch is slipping and is due for replacement. I'm wondering though, how does a worn out clutch plate cause the disengagement of the clutch to become stiffer/more difficult? How does this translate into an engagement point that eventually finds itself at the end of clutch pedal travel?

Would installing a new Sachs clutch kit immediately alleviate the stiffness of disengaging the clutch. What else would be needed to make clutch disengagement require less effort, and engage at a lower point?

Also, is it absolutely necessary to get a new flywheel? My mechanic was saying that resurfacing a flywheel is impossible on flywheels that are found on our cars(Dual-Mass flywheel?)

Thanks,
the Newb from Colorado