I'm not quite sure what you mean. Do you mean you want to replace part of the water pump?
Water pumps are cheap providing you've already got a genuine VW one. New ones are £50 from VW and if you return your old VW one they refund you £45.00
To get access to the water pump
remove driver side front wheel
remove splash guard
remove power steering belt - there is an adjuster to release the tension
remove alternator belt - lossen the 3 bolts on the aternator and lever / push down on the unit (its spring loaded) to release the tension and remove the belt
Remove the two pulleys
Unbolt the alternator - don't lose the spring
Unbolt the plate / cover which the alternator bolts on to which covers the water pump
You know have access to the pump.
Full, detailed guide here
http://faculty.ccp.edu/faculty/dreed/Campingart/jettatech/t-belt/index.htm