You need the correct harness to go from your original radio to the RNS-E. You have to remove the gauge cluster and add two pins and wiring to get CANbus communication down to the unit. I also installed the GPS antenna behind the cluster (it's a known spot for still getting good signal), and if done properly you have to remove and run a wire to a pin in one of the connectors under the driver's side kick panel for reverse signal.

There is also a known issue that the B5's have where the RNS-E will screen will flicker (something to do with a light sensor in the gauge cluster. The only fix is to replace your gauge cluster with a new one (has newer firmware). I did this cause my center LCD was messed up anyway.

The other issue is a clock/time communication problem with the RNS-E and the CANbus. The RNS-E won't keep the proper time so your trip times would be off when using the Nav. A guy has developed a box he calls "CANgate" which fixes this issue.

There's tons of info on it at this forum:

http://www.navplus.us/forums/

Total cost probably around $1500

RNS-E
GPS Antenna
Plug-n-play harness
OEM Pins for tapping into CANbus
Radio Antenna Adapter
CANgate


I did this when I had time, so little bits here and there. Probably spent about 12 hours total. Not necessarily for all the work, a bunch of time researching what I needed to do.