Just to make your job harder you want to get an ECU with at least one of the immobilizer keys that went with the car. Also make sure you get a receipt.
The reason for this is you will be able to start the car without taking it to a Honda/Acura dealer. To do that get a key cut for your car without an immobilizer then tape it to the immobilizer key from the donor car head to head. If you don’t do that a Honda/Acura dealer may not be able to reprogram the ECU for all keys lost as it requires the VIN of the donor car that could be removed from the Honda/Acura database. A Honda/Acura dealer should be able to add and delete keys if you have a working key.