Letting end user att nodes, problems

I am creating a module and for this module I also need a new node type.

Now the problem I don't quite know how to overcome is the following.
I want my end users to be able to edit and add new nodes of this type but only add change the node data, nothing else about the node. Also whenever an end user edits a node a revision is created so the administrator later can go in and roll back a change. Not completely unlike wikipedia.

The second thing is that it is important for this page that the user can edit a node from the page they are at rather then being redirected to a edit page. I need the edit form to show up in a thickbox (or similar) and then submitted via ajax.

If this can be done, then I have no real problems any more :-)