This site: http://www.mp3car.com/
may have some information for you too. There are a lot of Chinese companies that make video displays for dashboards that take HDMI and/or VGA inputs, and hardened 12VDC PC cases that are made for automotive use.
As for modifying the factory system, your time will be better spent working on an aftermarket system. Besides, the second your VW dealer sees what you've done, you can forget about the warranty.