If u tell them when activating, that the old mobo died, and it is comparable to the old one or the same one, MS will allow u to do the change.
But try to use high end while the old one was mobo $100 worth and it will be no-go.
I have a Z68MA-D2H-b3 that I'm about to RMA. I bought a Asrock Extreme 3 installed it and it activated automatically. I'm just sharing my experience.