Audio Systems: double din in dash dvd player, cadillac sts, double din dvd player

Question
I have a 2002 cadillac sts w/ bose system and i want to know if it's possible to add a double din dvd player(JVC). I was looking on the internet and the car had a optional navi system with a 6.5" screen factory. And the dvd i'm desiring also is a 6.5" screen. and I also want everything working, steering wheel control's, six disk cd changer, and onstar. I talked to a technician at one of the leading
audio stores in my area. And he told me with mdifications he provbably could do it. I would like a second opinion from an expert. Because even though my car is five years old i don't want it torn apart!!

Answer
to keep the steering wheel  controls and onstar i will go with a pioneer kenwwood or eclipse  there are interfaces from PAC and soundgate to do that   the cd changer only works with a gm radio and there is no adaptor or interface to make that work with any other radio
you will lose the cd changer
if you modified the dash a little the radio will fit