In essence, scripted vehicles rely on Lua and quite a bit of math to pull off realistic flight or wheeled-movement. It looks complex when you don't know what you're doing, but once you actually learn how to make your basic items, get an understanding of the engine's physics, and then learn scripting, it all clicks. I recommend that you just start modding simple things and gradually work on more complex mods, learn scripting at a comfortable pace, and you'll be able to make your own vehicles.

Just experiment and have fun, you don't need to rush at the things higher up. You'll get to them with time.