Adding Domain Controller 2012 to Domain 2003 w/Existing Exchange 2003

I have a single DC 2003 with a single exchange server 2003. I am currently running at domain/forest  2003 functional level. The plan is to introduce a new server with DC 2012 into the existing domain. The problem is I've heard if I introduce a new DC 2012 into my existing 2003 environment, the exchange server 2003 will break? Ultimately I plan on migrating email to Office 365 and upgrading our DC 2003 to a new server with DC 2012. HELP guru techs, what should my process be? If i put a new DC2012 into my existing environment right now, will I break my exchange 2003 box?

Thanks,