The only way to get in the big building where the main stuff is I found is the non-collisioned gate, only 1 side you can walk through.
No, there's a ladder around the far side from the side you start. It's just behind level with the back of the house, and partially hidden by some foliage.
Grass is very impressive. I only hope my grass looks half as good when I've actually put together a whole level with it.