The system you are looking for isn't really that difficult though the radar I would go with a V1(hasn't failed me yet). Everything else is and has been available for a while now. I wouldn't go with vista personally because of integration issues, but to each their own.
You can pickup a mac mini with a good processor, big HD, bluetooth controls for keyboard and mouse(or wii controller
) nav software is readily available. As far as the monitor goes you can relocate your OBC and run a 7" touchscreen monitor in that space or remove the radio and put a true double din in(climate controls are readily moved you just need to glass a face). Though with the Ddin I'm not familiar with computer integration with the touch screen.
Any other questions?