Surprised and flattered this still gets hits lol.. I have moved on to another car that pretty much has a "carPC" from the factory.. but I still own this car and the computer is still functioning although I rarely drive it ... I uninstalled the wireless EVDO router as i don't need it anymore in this day and age of smartphone tethering and USB based wireless internet.. actually I think the whole carPC thing has been obsoleted by smartphones. As good as iGuidance is, Google maps on a droid is superior.. and I can play video and music from droid.. pretty much anything the carpc could do.
As for cutting the lid.. I used a dremel.. I do recall taking some pics of the post cut lid.. but it was so long ago I can't really remember what i did.. it was trial and error though.. I'm at work right now but I'll see if I can dig up the old pics and post them.
This thread might help you a little..