Migration of Entire environment.. HELP!!! Tips, Tools, Tricks, or Advice!

Alright,

So I've been in my current position for slightly over 6 months and the day has nearly come when a project I had zero input on is about to be ready for deployment. Our CEO hired a "business consultant" to manage and plan a server and network upgrade, and I'm nearly ready to have to migrate my entire environment to a HaaS cloud environment. I'm currently already in "the cloud" with all of our servers sitting on a VMWare cluster in a Colo facility about 20 miles down the road. I currently have 26 VMs running all as Server 2003 Standard Edition and will be going to Server 2012 R2, other than relevant software installs and data migration, ANY ANY ANY tips, tools, or advice would be appreciated. I will admit to being terrified of this project both because I've never actually done this (I'm confident that I can just anxious about the...