I would do a search through the forum, as most of the questions you asked have been covered in the past. Also, if the factory unit offers CD Changer control, I would contact either Blaupunkt or Crutchfield to find if the standar Blaupunkt aux input adapter would work with your head unit. Also, if you are just looking for a prebuilt box, then check out www.phatnoise.com They are supposed to be shipping a unit this fall that will interface with most factory head units with changer control.
Good Luck! http://home.earthlink.net/~avgeek
[This message has been edited by AVGeek (edited 08-07-2000).]