The car sounds like it will be fun once you get it sorted out. The C320 should have the 240mm clutch disc which is slightly larger than the 228mm found in the C240, the dual mass flywheel may be the same. I also think that the crossfire uses the same trans, flywheel and clutch setup, but don't quote me on that. The dual mass flywheel has to be carefully inspected to determine if it will be good for continued service and not all machine shops can resurface one. The good news is that transmission and cluches on these cars are robust and can take a lot of abuse. I would try to pressure bleed the clutch and see if it starts working again before you start throwing money at it, its fast and easy to do, and at the very least you will be able to see which component is leaking.