Pre 2002 Radio Aux install

[ConorBurns]

Hey all, new to the forum here. I'm planning on installing an aux cord in an '01 X5. Now I know that you can get the factory/OEM kit with the cord, but I also know that only works with radios from like October 2002 and on? From what I can tell, the cord/wires are attached into the harness that plugs into the CD player, not the radio head unit.

My question: If I want to use a kit like that, then do I need both the head unit and CD player to be from 10/2002 onward? or just the Radio or just the CD player?

FWIW, its a non-nav optioned model with the Buisness CD it looks like. There's a few other threads circulating this issue, but the answer doesn't seem to be on any of them. Otherwise, is there a way the existing radios might actually work at all?