Those are the main steps indeed. You might also need to do something to install/configure the digipi+ and make sure squeezelite uses it as an output but that should be very straightforward as well (I have a similar set-up but I use bluetooth instead of an extra soundcard)
Be aware that the 2A adapter might be on the edge for this. I regularly had the „low power“ symbol when I first started working with the RPi3 and the touchscreen (different usage though, not max2play). I don’t understand why vendors don’t supply or at least advice for a 2,5A or a 3A PSU when buying the 7″ Touchscreen.