My 2004 9-3 currently has a single disc cd-changer. I have a 6-disc changer successfully divorced from a like 2004 9-3. I've heard a software upgrade via the Tech II is needed to ensure my current radio / audio recognizes the 6-disc changer so it functions correctly. Someone else said to just marry the 6-disc changer to my current radio / audio and it will work. I want to confirm what I need to do to swap the 6-disc into my car. Thank you!