Welcome!

The communication system in the latest model BMW's (from the last 18 months or so) is not the same as that in older models, which used a protocol called "I-Bus" for various non-essential components such as the radio, TV and Nav to talk to each other. In other words, it's very likely the new X3 you've ordered no longer uses I-Bus, however as sites such as this one are not up to date yet, you'll have to ask the question on this forum to be sure.

The discussions you've seen about a circuit board relate to ones such Rolf Resler's. These will work in older I-Bus vehicles only.

The older Dension IceLink adapters do not work in the new vehicles for the same reason. Dension have a new box called a Gateway 500 for newer non-iBus BMW's, which now use fibre-optics.

So my suggestion is to hang around a little and let someone else work out the new BMW communication protocol before you try anything.