$400 mill? I'd do two things.
1) I would sign a contract pledging twice as much money as Brent Feller each year with the stipulation that he's only allowed to attend games in Row 74 of Kinnick Stadium (not 75, so he's got someone's knees in his back) and he's outright banned from Carver and traveling on the team charter planes.
2) I'd make a ridiculous donation of like $20 million bucks to buy the Paca club level and only allow disadvantaged kids in it free of charge, no exceptions.
As an additional condition of my two donations above, each year for the nebraska game players get two helmets. Helmet #1 has a Tigerhawk on one side and a graphic of Keith Duncan blowing a kiss at Scott Frost on the other. Helmet #2 is the same only reversed, so that no matter which endzone we're defending we can switch helmets and Frost has to look at it the whole game. That would be in effect for as long as Frost is coaching, so really it'll only be a couple years...not a big deal.