As I was researching to install my video system, I found this link to the DIY Network where they apparently did this in a show, and used a MPV as the demonstration car. They have a summary of the steps with pictures on their website:

http://www.diynetwork.com/diy/shows_wkm/episode/0,2046,DIY_14348_32918,00.html

There are some good tips.