Depending on the mileage on the secondhand dash you got , as if you used a registerd version of the multiscan software and connecting cables it allows you to increase the mileage but not decrease, there may be other people out there that have the equipment that allows changing the mileage up or down, would think fiat would only be authorised to use new parts from them and why they stated that to you, there is someone from the netherlands that comes on here that is very handy with dashboards but you would have to send dash to him if he is available and capable of doing so.