Adding a touchscreen doesn't require you to do anything to make it work. You basically just swap monitors, and you can use UCCNC with the touchscreen.
Adding buttons is very simple in UCCNC. Just wire the buttons to your UC300ETH.
Using Input Triggers, you just enter the port and pin number of the button, and assign a function to it. No programming required.
An MPG is also easy to setup, as there are already settings in UCCNC for it.