None. Just fucking work hard, pick up heavy things and move snow with a shovel. Redneck skills do help (welding, heavy machinery, grinding, ect.), but aren't necessary and can be learned on the job most of the time if it's needed.
This. I'm guessing you'd need some education on top of a good amount of experience if you wanted to actually design the parks for big mountains, but as far digging goes, it's exactly as it sounds.
Show up, work hard, and don't complain about the weird hours. Other than that it can be super rewarding when you get to hit the features you just helped build.