New 2012 Active Directory Domain Setup, DNS Convention Question

I'm setting up a new Active Directory Network from scratch for a client
with 2 Server 2012 DCs. Haven't setup 2012 yet - first DC setup.

I've
always setup 1 office Active Directory Domains with just a 2nd DNS
namespace like "domain.local" - not "corp.domain.local". I'm not
familiar with setting up multiple offices and linking them up, etc.

With
this particular setup, it might be possible in the future that remote
offices will be linked to the internal domain in some fashion.

With that in mind, here are my questions:

1)
is it smarter to start the setup with a third domain namespace like
"corp" for the headquarters if you're going to have remote offices in
the future?
2) Or can you easily change it in the future so it doesn't matter right now?
3)
Also, I've seen on all of the Microsoft examples online that they're
only using ".com" for their internal domains, I know you can do this but
I've always just stuck with ".local" to keep things simple and
separate. With 2012, is there a change to this?

Thanks.