There are a few Focus installs around. Check out Stevieg's install. One of the most complex Focus installs. Wizz's install also features a flip down monitor for the passangers in the back.
This should be enough to get you started:
http://www.mp3car.com/vbulletin/sear...archid=1912511
http://www.mp3car.com/vbulletin/sear...archid=1912529