just finished doing mine, part is 8 quid form citroen, u need to:
jack car up
wheel off
undo ball joint bolt completly
pop the ball joint
pull the driveshaft out of gear box
use a large flat head to get the old one out with scratching/scoring the casing
put new one in, make sure it goes in straight as said use a large block of wood and put back together
i changed my gearbox oil while i was there aswell, u need 2lt of 80w and 8mm square socket if your going to do that
jobs a good un