Mary Elaine,
Carol and I used the DK Eyewitness Travel Guide for Paris about 10 years ago. I think it is a very good one. I would loan you ours but it is very dated, 10 years old, I would go to a book store and take a look at the current one.
Carol and I also used the Frommer guide but it is dated 2000 also.
I would think you could do Paris without a guide just a book or two.