You have to swap the glove box lock cylinder into a new glove box door if changing doors. You can get around this by swapping the handle but the handle might break. When you remove the lock cylinder from the glove box, put the key in the cylinder and this will help prevent the tumblers from falling out. This article shows how to replace them.
I put this on a separate page because the original page was too long and this shouldn't normally happen. If it does, refer to the below procedure. If you stumbled upon this page, please see 1000q: glove box door and handle repair first. This is a partial mirror of http://forums.vwvortex.com/zerothread?id=958556
Put all the pieces in a box because you will end up dropping some small
Inside the lock there are 3 parts: the lock cylinder, 3 lock tumblers, and 3 small springs. When removing the lock, note the orientation of the lock tumblers. Each tumbler has a number designated to it like a combination lock. This will be important in putting the lock back together. There are three thin slots inside the lock cylinder. At the bottom of each slot you will see that it is rounded. The springs go into the holes at the bottom of each slot.
Place the tumblers back into the slots. Place the narrower part of the tumbler in first. If you put it in incorrectly, the lock will not work. Try to note the orientation when they came out of the lock. This will help you with the installation of the tumblers. Place the tumblers in this direction like in this image.
Take your key and insert it into the lock. The tumblers inside of the lock should sit flush
in the lock cylinder. If they stick out, the tumblers are incorrect and
won't let the cylinder rotate when you turn the key.
This is the way the lock should look when the key is inserted, all the tumblers are flush which lets the lock cylinder rotate when you insert the key.
Keep the key in the lock. You can now insert the lock cylinder into your new door.