Work weirdness -- politics, antics, I need help with getting work savvy advice and learning about life!?

Did you tell them that you don't think that you can do it because you are not aware of any previous plans? I think it's a bit too late for that since you already accepted the project. So, what you can do is to keep asking questions whenever you are not sure about things. If possible make sure you ask the questions via email or anything that can be evidence. Express your concerns in writing (email) about different aspect of the project while you are doing it. If something goes wrong you can show all the email conversations. Those show that you did your best and what kind of support you got from your boss.