The body computer is chassis specific and can only be ordered through a dealer.
I have been told on many occasions that a second hand unit or one from another car cannot be used, again as this has to be programmed to your VIN.
Labour from either dealers or indy are at insane rates some are £55 per hour.
They cost £350 for the unit itself but you have to pay before the part is ordered.
If you order the part and try to fit yourself and it doesnt work then the stealers will blame you and say youve damaged the board - even if you know you havent.
As the part cannot be returned i would suggest pay them to fit it, they charge overall for the part and labour about £500, which is disgusting.
As stated in a post above, the main giveaway for a faulty body computer is the rear light failure, (generally the red) the light may stay on even with the ignition off.
I actually took my car to an auto electrition who piggy backed the wire from the opposite light to make it work correctly costing £198 but this didnt get rid of the warning light on the dash.
of course the body computer can make allsorts fail and make different warning lights come on, but in your case this does seem to be the likely cause.
Anyway back to the question of can you recode it through your general diagnostics.... no, you need a replacement unit.
*** however if someone can manage it then you will make a fortune because this is a common fault ***
WOOF BARK DONKEY!