It is real easy to install. What I did is actually phone up Dension - told them exaclty what my car's "config" was and they sent out the unit to me.

The most difficult part of the installation was getting switched power to the radioshack convertor. Once that was done the whole system is plug and play.
After that routing the cable to the front console takes about 15-20 mins. I had to drill a small hole in the cup holder area in order to get the actual cable in, but apart from that it really is easy to install.

I have an 01 X5 with DSP and Nav.