I actually bought the mono gear as a set and converted it to colour.

The head unit in your case seems to be a dumb display and some buttons. The only audio system therin is the tape deck that feeds line level audio to the BM24/BM54.

Wanted the add

3a) Check for cmpatibilty with your oddball system. Should be fine as it's based on the CD text display system.

4) Get a Dynavin E46-3G (v5) with the 5M FAKRA extension cable.

BTW, check your system, if it is the DVD version of the nav player (converted to colour) and the 40 pin BM54 tuner are worth £200-250 each on eBay.

I have a full E46 factory fitted nav loom with HK audio and BT harness sitting in a box at home, going on eBay one day.