Document endpoint for Create Document

Hey all..

I can get a document and put a document, but have never successfully POST a document. I need to take a document, change the name and create a new version using the API. I have a few questions:

Where do the GUIDs come from for the ID values?
The API doesn't show the data: branch of the JSON string in the help file...is that on purpose?
Does creating the Document automatically add the path? Or do you have to watch for that and do them as separate API calls before POST the doccument?

Thanks to anyone who can help.

Buck