Yep its a double din JVC head unit.
the os-2 can be had cheaper than what the site lists, the link is to the manufacturer and they just list the suggested retail. It's a bit more than just a harness, has a box to retain factory functionality of chimes / onstar.
The radio interface - you mean the steering wheel control adaptor? Yea i used an older one on my 1996 olds when i put a jvc headunit into it. Have to program it to get it setup. I could do more explaining but its simpler to just link the install pdf for one of them.
Swi-Jack Install pdf / 2004-2008 GP Vehicle specific install
Link for all the PAC modules for 2006 grand prix They make a module for pretty much everything....
This is what imean for an antenna adaptor, sure your extension didn't do this and you didnt realize it?
