Similar to Gail, I have recently wrapped up a few migrations. Going into every migration or upgrade with the client, the first thing and most frequent thing I will tell them is we need to have a test environment and we need to test the new server with the application.

A lot of time should be spent between the consultant and client in order to make sure they are going to be able to sustain business properly after the server change. There is plenty of documentation out there on what has changed, what is new and what has been deprecated.

If you need assistance, and similar to Gail, drop me a PM. Maybe if Gail is in the wrong region for you, I might be closer to you.