1. if you have a wizard with misty step they can just teleport in there, if you're positioned correctly you might be able to jump in there with the jump spell too.
2. you need one of those hag masks - put it on, and the illusion is revealed for your whole team and you can walk through it. There are four on the table by the first tree door.
Hint: if you don't want to be spoiled, have you noticed any unusual attire worn by the local residents?
