shouldn't be any issues. I know of a few folks with the US-based Nav in their 2001 A6 and they added the Nav+ (CD-based) without any problems.
A) you can mount a new GPS antenna inside your dash (see pix below); many with the RNS-E have gone this route
B) If you want to use your existing GPS antenna, you will need to run an extension wire to from the drivers' side trunk behind the RNS-E (a lot more work than it sounds); plus, some have stated that the older GPS antenna's don't work with the RNS-E (I'll let the others chime in)
Also, you should probably disconnect the power behind your old Nav drive in the trunk.
The RNS-E from a C5 A6 is what you want...see the pix from the forum from others.
Just my data dump...off the top of my head.
Good luck!
A) you can mount a new GPS antenna inside your dash (see pix below); many with the RNS-E have gone this route
B) If you want to use your existing GPS antenna, you will need to run an extension wire to from the drivers' side trunk behind the RNS-E (a lot more work than it sounds); plus, some have stated that the older GPS antenna's don't work with the RNS-E (I'll let the others chime in)
Also, you should probably disconnect the power behind your old Nav drive in the trunk.
The RNS-E from a C5 A6 is what you want...see the pix from the forum from others.
Just my data dump...off the top of my head.
Good luck!