I'm not familiar with 2008, so it may be a new thing that AD is REQUIRED as in integrated part of setting up users. That seems to be the gist of a book that I have, anyway. The servers I administer are all 2003. So once you mention AD you have to get involved with local DNS.
DNS CAN be involved if you're a core services provider for an ISP or something like that. Your setup should be pretty straightforward, like Wanderer mentions.
You were talking about your domain name selection. It's good for now, for a year, for two... What about five? I've lost track how many times I've planned a setup based on someone's list of needs, almost doubled it to be on the safe side, and then 4 months after implementation be asked, "We know we didn't ask for it, but can our setup do THIS?" And it can, because you've planned for that in your overhead.