Sadly I have the Business CD unit made by Blaupunkt. I tried to do something similar to that. I tried to find the line level wires from the CD unit to the main board. Plan was to connect my wires there and then cut the traces from the CD unit board. I didn't have my oscilloscope or multimeter with me so I used a little speaker to find those connector pins (risky method). I only found one pin with audio signal but I didn't get any sound to the speakers using that one. Maybe there is some offset in the signal? Anyway, I couldn't find datasheets for the CD player controller (Made by Technics. I found a datasheet from almost similar one but those output pins were not connected in this.) or the DSP made by Motorola. Harsh method would be to connect the wires straight to the final stage amplifier input but then I would lose sound settings and volume knob etc. so don't want to do that. I did a mod like this to another Blaupunkt unit from Mercedes and it was easy.
This one seems to be a bit more complicated or maybe I missed something obvious. I didn't find any information online about this. Usually CD players using pretty basic design because they can just copy paste it to another unit.