here's a detailed pdf of 150 pics.
link taken from this thread Ampie Case Guide by LexF15 in 1990 Celica ST
the components are similar to your setup.
the m2atx manual should have a wiring diagram for your reference.
most of your q's are covered in the faq section, http://www.mp3car.com/vbulletin/the-faq-emporium/
what car are you installing your carpc in ? if possible post a pic of ur dash.
btwn heres an indian source for carpc components, www.iRide.in