Which door would help with part number mate.
What's your symptoms?
Does it just not remote lock/unlock, does it try to? Is it opening with the key fine? etc...
For info, I did the drivers door on mine, bought part from eBay - non-genuine but did the job. Mine was a pain in the rear as I couldn't get the handle off at all and had to resort to sawing it and replacing it which was added fun. My problem was intermittent unlock via the remote, could hear it triggering when you pressed the button but sounded like it was straining to do anything.
Door skin needs to come off, recommend getting a friend to help you as it's a lot to hold up and align when you refit it and try to get the screws back in place, needs more that two hands really but can be done.
Its all just screws and bolts, you will need a set of torq bits and a spline bit.
Guide here on how to do it -
http://www.mk5golfgti.co.uk/forum/index.php?topic=34343.0