Hows it going guys, this may be slightly off topic but this seemed like the only place where my question would fit.

I've been playing guitar about 3 years now, and I recently got a job at my local music shop. I'm pretty knowledgeable when it comes to most string instruments, amps, accessories, and even band instruments. However, I'm completely ignorant when it comes to PA and lighting stuff. Whenever a person comes in I'm afraid to offer help for fear they may ask me about microphones or mixers or something else I have now clue about.

How would I go about giving myself a crash course on this stuff? I'm very interested in it and want to learn, I just don't know how to go about it (I would take a college class but I can't really spare the time right now). Does anyone have some good resources on the topic?
Wow, this looks like really good stuff. Thanks a bunch, Lee.