Collaboration

Hi,
I am initially impressed with your tool. I am running a class of 30 students who I would like to collaborate on writing a class set of notes. I have some questions:
1. How do we make the document available to just the class to edit?
2. Do they all need a separate login to get to the document and what is the easiest way for them to do this?
3. Someone mentioned history of editing - is this now available so you can see who has edited the document?

Where can I download an instruction manual or do you rely solely on forums?

Thanks