Well, for short answers. You can randomize something with varibles, but to make one arder than the other, you'll need a larger range than the range of numbers (don't know how to explain it...) And to go to a different map, in the event, you make it activate by pressing the action key, and then you tell it to 'Teleport to Map' or something like that.
These are both simple things, so maybe you should look for a begginer tutorial. Sorry if I wasn't any help.