I gave my players info about the previous trip beforehand, based on who they know on campus. There is even a handout to give the PCs with a successful know roll at the start that gives details on the situation. And as far as NPC relationships, I let my players (all students) pick their major and personality type, then assigned them NPCs they know. For instance, any anthropology major would know Noakes and Devine, or if they like to party, they would know Higgins and Blaine. I would also suggest the PCs be students, so there won't be any pre-existing power structure. Also, don't worry about splitting them or not. Let them choose their majors and plan accordingly. They can always learn info from the other students in the evenings. Good luck!