The blog at www.fredmiranda.com
is usually awesome, but I'll tell you, youtube is awesome if you know what you're looking to do. And Nikon has a ton out there. Hell, their mirror lock-up is still the best out there IMO, but that pretty advanced stuff right there (if you're doing stuff that needs it like shooting timed exposures of stars).
But here's an article for how to set it on you D3100: http://www.dummies.com/how-to/conten...kon-d3100.html
The key are the subjects you search for on youtube. In this case look for youtube videos for the D3100's white balance. Even though the concept is the same across all cameras, the procedure is pretty specific to a brand, so it'll save time. The key will be to understand why you're setting white balance. Photo nerds like to talk smart and call/say different kinds of light have different temperatures/warmth. Whatever, it's all about photons! But alas, all folks need to know is that when you shoot under florescent lights you might get a blue tone, and in some cases green tones! You don't want that, so here's what you can do..... So white balance "the subject" is worth a 5-10 minute video. Once you've heard the nerds talk, the important part is how do deal with it using your super-smart camera.
But the concepts of using AV for a camera that you've dropped a 2.8 lens on, that's just something that you do and it's pretty simple - set the camera to AV, set the ISO to something really fast, then shoot. The concept is to use the "bright" 2.8 lens, and the easiest way to do that is to use AV. See, I'm more lazy than smart.
Here's a tutorial of AV/DoF (Depth of Field) that's worth a few minutes of your empoyer's time and his bandwidth..