Almost without a doubt.
Remember, George even sued over Battlestar Galactica... which while stylistically similar to Star Wars, really didn't borrow that much from it.
The problem is the concept art is still very recongnizably Darth Vader. And then there is the issue of the character himself, is he a dilapidated old man who has to wear the suit to keep him alive?
If you don't ever plan to publish your story, then you really have nothing to worry about though.