I went to jazz fest two years ago, if there is a big name band you want to see stake out a spot early. Bring a blanket for the field and plenty of water, it was in the 90's when I was there.
Have you been to the street fests in Chicago in the summer? It is similar but on a much larger scale. There are booths with everything from art to jug band instruments to souvenirs.
You have been to New Orleans so you know how good the food is and there is plenty at the jazzfest.
We stayed in Metarie and drove there, if you are flying I remember there being a lot of cabs to get you to the fair grounds.
This site had a lot of valuable info. Right now they have a tentative list of who is playing, as it gets closer they have times schedules for all the stages (14 if I remember correctly)
Have a great time! I am thinking of going myself.