I just stumbled on this thread and wanted to report a couple things.
Yes, there is RV parking at Lambeau VERY near the stadium itself. Its cheap too, but you have to get there at least the day before the game. You wont likely find a spot on game day.
You do need to be willing to stay with your RV or leave it there, but they dont charge you for anything until game day.
Two, this location has BIG approved plans. 2016 could very well be the last days of RV parking anywhere near the stadium. It's an awesome experience, so if you have been thinking about it...DO IT IN 2016!