I am working on very much the same project in my car. Curently I have LinuxICE installed which is a stripped down version of Ubuntu with NGhost installed for a nice front end to handle music/video/gps.
I have a 7" lcd that I put in place of my head unit, the problem I am having right now is that I can just barely see it in the daylight without my sunglasses on
. Looks great at night! I have a Lilliput EBY701. I didn't have to actually make any modifications to my dash to fit it in, except for mounting brackets of course.
I have a desktop pc sitting in the trunk as my computer for the moment, though it sucks more power than I want to think about. I keep blowing this 40 amp fuse when trying to recharge the secondary battery and run the computer...
Oh, I have the OBDII interface from scantool.net also. I haven't gotten it set up yet though. I got to the point of using minicom inside linux to see the data being sent out but failed in getting a program to make sense of it
.
Here is my thread I started on my project.
http://www.gassavers.org/showthread.php?t=5233