Inner or Outer CV-joint??
In any case, it's a very messy job to re-build or even just re-pack a CV-joint...
One of the TDI-Gurus here recommends replacing just the bad CV-joint over replacing the entire driveshaft... Pete says that the OEM quality driveshaft is far superior to the commercially available replacements... I've never had reason to doubt anything he says about TDI's...
If you're into getting down and dirty... you'll need to remove the driveshaft and take apart the questionable CV-joint... after cleaning everything, you inspect the balls and races to see if there's any physical damage... if there is, you must replace the joint... if not, just re-pack with Molybdenum Disulfite CV-Joint grease and replace the boot... you can get a boot kit from the dealership (or, I imagine, Impex)...
Good luck,
Yuri.
PS: Glad you got your TB belt changed by one of the Gurus here !!!!!!!!