For now, just know how to do it, no need to understand haha. Even myself who has just started this don't understand why you subtract 180 etc, but i think its got to do something with the revolution of the circle on the point etc.
Yep it is hard, most people tend to do a science degree or something related to the course first, but you can do any degree and still get in. On top of that you need to sit the GAMSAT as well.