The ticket I had - a paper ticket with travel on two airlines - meant that I had to go out to LaGuardia to even find out what the fare difference would be. It turned out that the difference was the cost of another ticket, so that idea went out the window. After discussion, they decided to keep me in NYC Sunday as well since there was a likelihood that I might have to go back to Scranton that day.
The result was a little serendipitous: the airfare was enough cheaper that it paid for the extra night's hotel room. So, I'm flying back Monday, and getting in pretty late that evening. At least I'll be home for my birthday.