What sensor are they talking about? a tyre pressure gauge?
I was told that the flat tyre monitor runs off the abs sensors so there is no issues with changing tyres (i went from runflats to non-runflats) and have had them on for 45000+km's with no issues.
The M3 obviously comes with non-runflats (from the factory) so i don't see any issues with just a normal tyre change