I have a Nikon D3100 also and love it. I also have a 55-200 and 70-300, I find that I use the 70-300 a lot more for animals,birds etc.
As far as info, you should have a disc that came with your camera that will allow you to print a reference manual. Take the time to print it out (about 200 pages) and read it. It is easier to understand than the user manual and will be a big help to you. The main thing is to keep shooting and do not be afraid to experiment. Have fun.

I am not blaming ebay, i have bought other things there and been OK
I blame myself for taking it for granted that everyone knows the difference between a circular (digital) and linear filter. Like everyone else I am trying to save a few bucks,should have bought it new.

Just bought a polarizer on ebay that was supposed to be circular polarizer, even e-mailed seller to ask. What I found out was that some people consider a circular polarizer to be round as opposed to a linear polarizer. Be sure you are getting what you think you are, at least it was an inexpensive lesson.