Rav4 Rav4 2015 XA40 replacement ECU and speedometer

[D74]

Hey,
I've got a customer wanting to replace both ECU and the speedometer on Toyota RAV4 2015, they're both from the same donor vehicle. I know I don't have the tools to program either of these, so the question is, if I replace these, is there a possibility of any problems arising? I assume the odometer will read the mileage from the donor vehicle, and that the customer might also need the keys from the donor vehicle aswell? Anything that might fall out of sync, or even worse, a problem that can't be reversed with putting the original ECU/speedo back?

Any input would be greatly appreciated.

[D74]

Anyone?...