I am working with some folk who are using Expression Engine Version 2. something. They are considering upgrading to the latest version. I know that version 2 and version 3 have a different directory setup. Is there any definitive docs on how to upgrade with minimal pain? Tutorials? Plugins? How to videos? I'm in the exploratory phase of this project and will appreciate any input on upgrading EE from 2.... to 3.0 - 4.0 and beyond!