There is value to a guided tour. My wife and I spend a good bit of time in the French Quarter. I have listened to the tour guides. They are entertaining, and can answer your questions. They can also provide specialized tours (like ghost tours). They are licensed by the City of New Orleans, and are required to know what they are talking about.
New Orleans can be pretty cold in January, with the wind coming off the river. Check the local weather forecast before you leave your coats behind.