Sat Nav retro fit -what is required?

[Kenquattro]

My A8 does not have the factory optional extra of sat nav. If I was to consider fitting the RNS-D unit, what else would be required? My car is fitted with Symphony 2 with the front load 6 cd and Bose. I realise I would need a CD Changer for the boot, along with the bracket and boot trim with the bulge. I also realise the RNS-E is a better unit, and have had both the RNS-D and RNS-E factory fitted in previous cars. However, I wouldn't be using the sat nav bit, just as I never did in both my previous A6s fitted with these units. My Tom Tom is a lot quicker/easier to use for that. My car is a March 2002 A8 D2.