The whole process looks pretty complicated to me-- the most I've done with my car stereo is install an old CD player, and by install I mean "watched my friend do it." But Andrew's writeup is really thorough, and he goes through everything from choosing components to creating a layout, to potential problems during installation, and what he plans to do next. Apparently the Mini is almost tailormade for car systems like this-- not only is there a special cable built to power it in the car, but there is even a special version of Front Row designed to be controlled from a touchscreen. Not everything worked well, however-- the Mini had a grounding problem, apparently, and Andrew had an issue with the Mini's volume setting reverting after a restart, but he was able to punch out an Applescript to fix it.
The end product looks great-- Andrew says he's still working on the mounts, but considering he's got a working touchscreen controlling a Mac Mini in his Corvette, that's good enough for me. Very nice.