Clutch or Release Bearring problem???

I have a 98 Vectra 2,5, I recently noticed that the clutch is giving me
problems when changing gears. When I release the clutch there's a noticeable
"thud" noise and you can feel the clutch bite sharply along with the noise.
It sometimes crashes when changing gears. Is this the release bearing going
or clutch about to pack in? What kind of price would I be looking at to
repair either of the above?
Thanx Simon

 

Sounds more like muck or something on the splines for the release plate, or
perhaps something wrong with the clutch cover. need to get someone to have a
look in that case.

Unless it's a simple case of a frayed cable, which you might be able to spot
for yourself.