There is $20 parking Juniper Rd off of Douglas at the North end of campus. From there it is about a 10 minute walk through campus to get to the stadium. As far as what time to arrive, that depends on what you want to do. You can tailgate in lot, if that is something you're interested in. Otherwise, I would recommend getting there no later that 1:30 to make sure you get a spot that isn't too far away and to give yourself time to take in Notre Dame on a college football Saturday.
There are food vendors around the stadium, library, ect, but I recommend steak sandwiches at the Knights of Columbus.
Dining // Game Day // University of Notre Dame
Make sure you're outside of the stadium 45-60 min before the game to see the band march into the stadium.
Enjoy!