Firstly, there is no "upper level" at Lambeau Field. If you've never been here, you cannot shy away from buying a seat in the 300s or 400s because the view may even be better from those sections and you can still make out all of the players from those seats. Additionally, you'll be able to see the defensive and offensive sets from 425 as well. It really is a section that appeals more to the fan that likes the X's and O's and doesn't necessarily have to sit next to the field.

It was a very small section which I appreciated and maybe only 15 seats per row so it wasn't a headache to get to the bathroom, every seat is close to the aisle.
If there is one food item that you must have when visiting Lambeau, it would be the bratwurst from Meat Packing Company or the Cheese Curds from Curley's. Goin' Deep Pizza isn't too shabby either. There are a lot of activities to occupy your time at Lambeau, just get to the stadium early on in the day.