So, I have a TDI SE, no nav.... I currently use a Garmin, but would like to upgrade to a RNS 510... what exactly do I need, and has anyone done this on a B7?
I'd probably start with a VAG-COM and a NAV unit.
The rest is pure work.
I'm currently trying to do the same thing, and honestly, I really doubt its that difficult, the Jetta guys, and Golf/GTI peeps do this all the time. The key here is to get a RNS-510 of the G series, as that is the newest North American Unit, and if you are getting anything older you will not get the newest features as the software/firmware, can only be upgraded on the A/B/C units to sw ver. 1040 (it might be 1140 can't remember exactly), and G series has software/firmware ver 3696, as well as a new GUI, 40GB hdd, LED Display, and support for 2TB SDXD cards. The only issue here is that to find one for under $1600 is almost impossible right now...
From my perspective, this is NOT an upgrade. I bought the TDI SEL largely BECAUSE of the NAV and media handling. But, my $90 TomTom (got free with purchase of tires) and my $300 Garmin (b'day present) are FAR SUPERIOR to the nav system in the 510. They are more intuitive, MUCH FASTER, and MUCH MUCH MORE ACCURATE than the 510 system.
I have a $30 Sansa clip mp3 player that handles music files far easier. If I had it all to do over again, I would definitely NOT get the SEL for the 510 system. My advise is you might want to find another aftermarket that will fit.