On a series 2 v36, $12k in bits and time. Using local NEW PARTS from the local g37 to do it. Not a used item from a wreck overseas.
We have been down this road on the phone and on forums. The vast amount of people will spend $1-200 on this idea few will spend $4k none will spend $10k. Some will try rudely to get the part numbers off me and get told no.
There is no cheap way out. The hacks the were done originally on the 35 series systems had a habit of reverting to boot loader due to a glitch in the hardware. Apply that same glitch to a part the RUNS the car via 3 network LANs and you are asking for trouble or even better a lawsuit when the system fails, stalls the car in an intersection and at worst gets someone hurt. Extreme case but entirely possible.