I would like to install my n810 where the satnav screen is in my xkr and have it running carman, canola and USB host to my 320GB WD Passport drive. Would also like it to replace my arcane Motorola phone interface to control my n95 via bluetooth using the touchscreen on my n810.

First, I need to find out the wiring of my XKR, then I need to know whether Canola2 can handle 50,000 tracks?

Let me know if you have tried anything similar and have any tips.

If you have the time and money to invest in this project, you might consider picking up a Beagle Board and some kind of Xenarc touchscreen.

This has the advantage of offering both forward compatibility (it'll be able to run Fremantle without much issue), more expandability, much more power, and a much more integrated interface.

This, of course, assumes that you're willing and able to invest some time in setting things up (especially software, which isn't especially user-friendly off the line), and getting the hardware together, but you'll get a much better experience when it's all said and done.

I was looking around at Beagle things and came across this http://www.beaglesride.org/ which is probably one of the initiatives the General is talking about.
Good luck I would love to see a nice Maemo car computer built into a high end vehicle.