Coupling

Moin, own a Volvo C30 bj 2007 that now cracks the 300,000. Hand-operated 2.0 diesel. Never had any problems! Now the clutch seems to say goodbye (maybe also normal that is worn after the km). If I step through the clutch pedal completely, then it shakes quite energetically. But only when it has completely penetrated. Since then I do not step this to 100% to change gears. Is also recently the problem. How harmful is this for the car? s I immediately replace a complete coupling, or is it just a particular component of the coupling, which one can replace. Because I ask myself whether it would be worthwhile to replace a complete coupling, which certainly will not be cheap !?