I don't intend this to be a Nikon / Sony pissing match, however I strongly recommend that the OP look at the list of features of both of the cameras that he is considering and make up his own mind as to what features are important to him and what are not. I realize you have stated that you aren't fully informed on camera features so please feel free to ask on this board and people will be glad to help you understand what they mean. I say this because I personally don't consider some of the features mentioned to be true features, and I'll stop there.
Also, whatever choice you make don't make the mistake of waiting until the last moment. Give yourself a few weeks and several hundred shots to make sure everything works properly, it isn't going to break, and you have time to get it back from a warranty service center if it does break.
Thanks, because I am still learning and trying to understand the features it so hard to understand what I am buying I have been looking for a few weeks now, I know I am not to bothered about video as a feature , Just great pics with the ability buy diff lenses in the future,also quality of lenses and ascessories, reliable tried and tested, I reviewed the d3100 against the d3200 and also the d5100, and the write up on the d3100 was still really good so I felt it wasn't worth the price jump unless it was a d7000, It's a lot to take in but I know I will enjoy learning, I didn't feel there was a lot on the net about the sony a37 so I wanted to keep an open mind, Ill get a zoom lense when I get either or... arghhhhh!