Hi - the site Stephen pointed to is a great resource for you. Based on the experience that we went through, the order I'd do things:
System Admins and Group Admins/Super Users go through the layout templates. Workfront did copy over classic ones into NWE, but really we found that we were things that needed to be done for each one. So we decided to start from scratch and really focus on which layouts we needed and what was needed for each. Basically it was two for each agency in our instance (a PM one and a Team Member one) with just a few additional ones needed. We also wanted to make sure we didn't take up too much of the top nav, so created a Dashboard of important dashboards that then added to the top nav so they could easily see what they should visit without losing the ability for them to pin stuff to the top. (Hope that makes sense)
When introducing NWE, just talk about navigation difference at first. The biggest thing people get upset about is that they "can't find anything." So I would suggest just focusing on navigation differences for the first meeting/training sessions: Main Menu, Left Nav, icons on the toolbar. [Side note: I'd also mention filters. I believe the default for Portfolios is My Projects but most of the people go to a portfolio to see all the project for a portfolio. Just mention upfront that they need to change the filter to Active or Current, whatever you call it in your instance.]
After you have done that, and they have had a little time in NWE, then you can talk about the newer features: Pinning to the top nav, rearranging the left nav, the Summary Panel for tasks and Documents, etc. We have everything on a centralized wiki so I usually send them the second link a week after I moved them over. If you are doing live trainings, not sure if a week later is possible, but try to do it close to when you did the first training.
