It's as easy as any other SW upgrade to the RNS-E - insert the new disc and wait!
Following advice from an Audi Tech I had the engine running to keep the supply voltage to the RNS-E OK, inserted the Western Europe DVD (DVD 1), the first phase of the SW upgrade started automatically (after a few seconds of the screen showing "Insert Navigation disc"), the RNS-E re-started automatically and the second phase of the SW upgrade started automatically, then the RNS-E switched off so I waited a few seconds and turned it back on to find it running SW 0550 and the TMC data gradually appearing in the INFO screen. I had to turn TP back on because it had turned that off, but every other setup was as I had it.
One other person who has done the upgrade has reported (on
www.navplus.us) that his RNS-E asked for the 4 digit PIN code, but mine didn't.
IMHO it's so easy there's no need for it to be a dealer job - anyway it's NOT a dealer job in any other country in Europe and they will be getting UK TMC functionality the same as us!!!
BTW Audi didn't take the opportunity to fix another couple of bugs in the RNS-E that DID get fixed in the US 2007 RNS-E DVD (when in MIX mode pressing FF exits mix, and better use of the top 2 lines of the DIS to show more of the song title - both fixed with US SW 0150 on the US 2007 DVD but both unchanged with EU SW 0550 on the EU 2007 DVDs).