If its the same genre, its likely to be an easier task. I recently got a call for a gig just 6 hours before hand, and the set list was 80% stuff I hadn't played before. But almost all of it was material I was familiar with, popular stuff played by lots of locals bands. I was pretty anxious going into it, really nervous.
I did my best to listen to the songs thru the afternoon and on the way to the gig. Turned out ok, not as good as it would be if had the time to really work them up. But I kept time, added some extra stuff where appropriate and comfortable, and had no train wrecks. It was a great learning experience, and did wonders for my confidence.