It is not a straight swap.
I have (somewhere) the wiring diagram to do this which I purchased from ebay (italy). No idea where I've put it though
Having previously retrofitted the full sat nav/DSP/Telephone/Changer monte in a 166 which included making a lot of the loom from scratch, then I have to say that the instructions were not that daunting to be honest - although a virtual strip out of the seats, lower console, some headlining (not as bad if you have the sky dome) would put a lot of people off.
tarqs is correct re price - the cheapest currently in the cars homeland on ebay is £250.
The other thing you need to do (which was not a requirement on the 166) would be to wire in a time-delay for it to power-up to avoid upsetting the canbus body ecu.
Definitely do-able if you can find the kit (WITH THE CODE!!!!) for the right price and have the time & patience (the 166 took the best part of 2 weekends to do it properly).
If I do ever track down a reasonably priced unit then I personally will go for it probably for the hell of doing it........ but if before then Mirrorlink ever gets there ar$e in gear and finally starts to cover windows phones as they have been promising for the last 18 months then I'll be going down that route instead.