moving OS X server to new IP address

Hey all, One of my clients is moving offices this weekend and I'll need to set up their server on the new IP. They're currently running internal DNS, POP & IMAP mail, file services, and WebDAV for iCal. The consultant who set up the box is telling me that config files and user settings need to be changed--and "in the right order." This is news to me, as I figured I could just reconfigure DNS, and change the hostnames in the Server Settings app. Am I missing something major here? Thanks again, Noam