Certainly examine the roots of SW in myths/fables/classic adventure literature and classic film serials. Then look at the development of Lucas in the film industry and as a filmmaker. These are very important to the development and overall appeal of the film.

I remember doing my thesis and it was a film thesis specifically for my degree. The idea that you must be critical whilst referencing sources and writing in essence a research paper is the stupidest and most inane thing ever devised. The two parts contradict each other completely. If your paper starts to look different to what you originally envisioned, don't worry. In the end, you can't really go into much that shows deep thought. That would contradict the research. Your final result will be rather homogenized unfortunately. But this is coming from the guy whose thesis included 7+ pages on how James Bond's sexual appetite defined his humanity and failings.

Just remember to have fun with it. Break it apart into sections to work on and then work on connecting the sections together into a cohesive "saga".