I had to do a similar thing back in junior high. We had to write a letter in block format to a celebrity. I wrote a very nice letter to John Williams, praising him and asking him some questions. I asked if he would write back personally.
I got a form letter from one of his secretaries, along with a little question and answer packet.
So if I couldn't even get a reply from John Williams, I doubt George Lucas even thinks about reading fan mail.