1. Can the engine be turned over by "Hand"? If not engone may need to be dismantled.
2. The ECU would be a Bosch EDC MS6 - 3. I have never looked for this item specifically, but ECUs for the con temporary 2.8jtd are available on Ebay, where there was a French company offering plug & play ECUs, not needing coded key.
3. For a replacement ECU, I would start thinking £150 upwards.
4, If you want to retain the key code feature, that would need the ECU recoded by a vehicle locksmith. Their time does not come for a pittance. Alternatively you could buy a complete set of matching locks, keys, code receiver, and ECU.
5. For ECU part number, you could try putting the VIN into
ePER. See top of page.
When I had to make two attempts to start my 2.8jtd last year, I considered carrying a plug and play ECU for emergency use. Last March when testing failures were 2 out of 5. I disconnected the code receiver and applied contact cleaner to the aerial connector. No subsequent failures.
I think that it would be a waste of my time to suggest more, until you research the options, and decide on a course of action.