"JasonS" & Wrath" have done this, think the faceplates are very similar (if not the same) in the B6 as in the B7, could drop either of them a PM and they might be able to offer some guidance.
Think the faceplates are just held on by small screws, just have to be careful and use the correct size driver and not round them off. Finding faceplates to buy can be tricky though... not sure if you can even buy them on their own direct from Audi?
Also a RNS-E unit from a Seat Exeo HU should fit without the need for a faceplate swap.