Yes true , but the Original poster has not put what year and what head unit he had before upgrade .
I've asked him some questions and still awaiting a response .
I terms of the optical communications only the ICM 2/3 had optics with the icm 2 having an amp under the passenger seat ( uk spec ) and icm 3 having the same plus amp in boot .
If it's a icm 1 then no optics .
But in all cases it's the atchual EHU which lives behind the CD player that has to remain . To give warning sounds .
In the original posters situation, if indeed it is a pre facelift dashboard, and that the new head unit was installed professionally, and he paid for the install , then in my mind he should take it back and ask the installer to sort it out .
But also I would like to know what was taken out ,
If it's a post face lift dashboard, then no problems with replacing as no optics were involved as I've done the swapp myself with no issues.
But until the poster replys, then we have no clue as to how to help him .