Thanks to all for your advice. The game is the Penn State-Nebraska game on September 14th, when the huge red Nebraska horde will descend upon the area. As one of those folks for many years, I have no doubt the hotels in the area really are sold out (although I now plan to check again periodically). Nebraska fans travel at the drop of a hat and don't miss opportunities to go to these sorts of games. I am aware of many people going.
The good news is that they just set the kickoff for 8pm EST, which means that we have the whole day to get there if we stay in Harrisburg. Getting back to Harrisburg at midnight will not be fun, however. If anyone is familiar with the towns between Harrisburg and Penn State, please email me privately. I'm thinking that staying somewhere along that road may be the best bet.
Thanks again.