Next question, can't a second hand ECU be used or does it need to be new or virginised like other replacement ECUs in the car

I don't think it is necessary to virginise the ABS ECU. It's not contain any immo data.
Also I think about the fluid question and It can't come out because the those "pins" what is visible on the disassembled module without ECU are only the coils and the "holes" on the ECU are the solenoids. So the system should be closed on thet point otherwise the complete electrical connection will be flodded by oil.
Maybe I will try to cahnge the ECU only. In the FiatEcuscan I can change the type of the ECU.