I don't mean any disrespect, but it sounds like the fault is in two hands: yours and the organization's. If you're at all uncomfortable with some of your assignments because of a lack of a rule book, look into getting one. However, if your organization does not properly prepare you, then they're at just as much fault, as they are pretty much hanging you out to dry.
If I'm not prepared to call a certain level of game or a particular rule book, I make it known to those trying to assign me. There's a reason why I only call ASA slow pitch: I don't bother with the fast pitch or modified rules.
See if you can get a rule book for LL. It'll keep you from nightmare situations.