Well considering Burtt, Lucas, Hamill et all only really are recorded speaking about the films on official LFL documentaries and such you wont find too much dirt. What little there is is mostly in print anyway, and really, there isn't a whole lot of dirt on the series.

If you are interested in an actual, true behind-the-scenes account of the making of the saga and its storyline, ie with regards to backstory, prequels and sequels, I am working on material for a book on the subject which should be completed in the next month or so.