The UI is pretty intuitive and they are making regular usability updates. Many things on the car are automatic so you don't have to mess with controls anyway, such as windshield wipers, lights, seat position, etc.
No, I don't. The Model 3 still has volume and toggle knobs on the wheel, so you can adjust audio without looking. Similarly to other cars, you have to look for a sec if you want to do something more complex. But it's not really a problem at all.