i'd imagine it's ok. why don't you ask your history teacher. you might find you have too much information on him but then you could jsut give dates in your title like from when he was 20 to 30 or whatever
You should be ok to do a writer. While it should be easy to get loads of information on J.D. Salinger, you will have to focus on ONE particular aspect, as the whole idea behind the Research Essay, is that it involves in-depth research.