...Is it an easy job to do?
lol, that is of course subjective
I have done one with the driveshaft in situ but its muuuuuuuuch easier off the car as the clip on the back of the CV is a bit a a git...
In-situ... Unbolt the star drive (8mm or 10mm I think, can't remember) bolts holding the joint to the gearbox drive flange... there is a 'circlip' on the end of the shafy that normal circlip pliers don't work on so remove that
Gently tap the joint off being very careful to hold the joint at 90 degrees to the drive shaft, it will extend back while tapping but as long as its straight it won't fall apart... the minute you have a slight angle on the joint the balls will drop (fnarr) out and you joint will fall apart... it can be rebuilt with a bit of patience (having done this myself!) but its a royal PITA so best avoid
Once the joint is off there is a dished washer that must go back on dish facing away from the joint otherwise you will not be able to get the circlip back on....
Slide off old gaiter, and refit the reverse... fit new cork gasket gaiter side of the joint (its recessed), add grease etc, tap joint back on, refit clip, bolt back on drive flange
Easier with the whole drive shaft removed but can be done in situ
<tuffty/>