This is insane. I have no idea where to start I tried shooting in manual mode and playing around with some exposure and ISO settings. because I dont want to flash my 2 week old in the face and there is not a whole lot of light in the room daytime and it comes out on the camera as a black image.
I got a PNY class 10 16gb card now just have to figure out to shoot in RAW format
I have not seen the 3100 yet BUT I am going to assume it is similar to the D70s I have as far as the menus and stuff goes. What I would suggest you do is shoot in NEF + JPEG mode. Nef = RAW. if you do both you can look at the images right away as JPEGs and then process the RAW versions.
I would also suggest you get something and put it on the floor on a baby blanket and practice. Take at least 3 pictures of the same thing one apature priority, one shutter priority, and one on auto mode. then compare the 3 on your computer and make notes of what you should try with the next one. The coold thing about digital is that you don't run out of film LOL!
you should propbably look at a shoe flash as well Nikon makes a SB600, SB800 and SB900. I have the SB600 and it does what I need it to. I bought it because it was cheaper than the SB800 and the 900 hadn't been released yet. but the light can be angled up or down which is good for keeping reflections out of glass and lights out of the babies eyes. I practiced some with the apature and shutter priority when the grandbaby was asleep:
I just set the camera down on the floor and adjusted between shots