I did a project like this years ago - changing from 4 to 5 digits across multiple sites. While you're focusing on the technology aspect, don't lose sight of the "soft" side. Your budget should include monies for new biz cards, letterhead, web page redesign (or anyplace individual extensions may be published)etc. One of the biggest gotchas, as ridiculous as it sounds, is printing and distributing new faceplates. Don't forget training and publishing to your employees. I used a faceplate program from Impact Technologies - and I forgot to include it in the budget. I'm sure others will have many good technology hints and tips for you, but don't forget the human aspect.
