Wiring a line in to the Mach Headunit?

I saw this cardomain page where this guy has hardwired a line in plug to his mach headunit, I have searched but never could find instructions....this is the cardomain page...about halfway down you'll see it.

http://www.cardomain.com/memberpage/349380

If anybody had a link to the instructions i'd appreciate it! Thx
-Chris

I found this part which plugs into the CD changer and found another forum thread, which says it will work, it plugs into the back of your mach headunit, then has RCA in, which can be easily converted. You press the CD Button once to get your cd's to play, press it a second time to get the aux. input.

http://store.yahoo.com/logjam/piefrdnaux.html

If anybody around northwest florida wants one of these (i'm using it for my xm radio, but can be used for a mp3 player or such), we could save on shipping (shipping is 10%)