Upgrade exchange 2003 to 2010, 2003 has no internet facing server (no mobile access)
I'm planning an exchange 2003 to 2010 coexistence to full migration.
I currently have no mobile/internet users. I have just exchange 2003 and exchange smtp delivery gateways. I have no front end server for my internal owa users (yes, you can actually have that configuration and still use owa, it's some kind of loophole in Exchange 2003).
I assume internet facing exchange will be required for 2010.
How should I proceed, and which roles should I install first?
I have my sans certificate from Digicert ready but unpopulated.