Shimano Di2 Synchro Shift Explained
A very cool feature of the new Di2 is Synchro-Shift. This will allow you to have the Di2 select gears appropriate to your cadence with the click of only one lever. See a video here https://www.youtube.com/watch?v=P0pIqlOWpqE&t=15s
Changing a Tyre
Changing a tyre is no big deal, you are going to get a bit dirty but it should be something you get familiar with doing and doesn't cause too much stress.
Here is a great video to show you how to do a change of tyre while you are out riding.