I just gotta jump in here. By all means, go to Nürnberg and spend the night inside the walls of the Altstadt. You won't have a lot of time for touristy things, but the area is pretty compact and you will be able to walk around and get a good taste (literally and figuratively) of this lovely walled city.
This Wikipedia article is pretty good -- http://en.wikipedia.org/wiki/Nuremberg, as is the list of things to see and do on Trip Advisor. The hard part will be picking which. I would pick the castle and/or Albrecht Dürer's house and one significant WWII site.
I lived in Nürnberg for 3 years back in the early 80's. I went back for a day trip from Munich in 2009. It wasn't nearly enough time to show my husband what I wanted to show him or to eat what I wanted to eat.
Nürnberg did rebuild after WWII. There is a great book that I bought while there, Nürnberg damals -- heute, by Ray D'Addario. It consists of photographs of locations after the war and later, after the rebuilding, taken from the same spot. The destruction was incredible, but so was the rebuild. If you can find it in a library before you go, it will be well worth the effort.
I'm sure others will recommend other places, but with a short time there, I would go to the Bratwursthäusle (Bratwurst House) -- http://die-nuernberger-bratwurst.de/index.php?id=3821 -- for Nürnberger bratwürst. Here you can choose how many you want and with what sides. They cook them over a grill inside. It is just off the main (Hauptmarkt) square.
The other franconian dish I fell in love with when I lived there was Schäufele (cut from the shoulder of pork, served with potato dumpling and franconian beer sauce). Beware, most places serve huge portions of this. Some places have it only on certain days. Ask your hotel staff for a good place to go for it. I've never had a bad Schäufele, but I'm sure it's possible.
We went to Der Barfüsser (http://www.barfuesser-nuernberg.de/english.html) , even though it has uneven reviews on Trip Advisor. I don't drink, but they brew their own beer and my husband thought it was good. He definitely agreed that the Schäufele there was great. Click on the English option and on the various menus under Speisen and Getränke. There are lots of good pictures under Galerie.