Getting a Nikon D3100 today - Do I need a stabilizer?

So I'm getting this camera today, and I was really excited about the video mode. I keep hearing that you don't have full manual control in video mode, and that the rolling shutter & "jello effect" is still a huge problem. Many people say they got a stabilizer and it helps a lot.

Can someone tell me what exactly a stabilizer is/does? Is it just for the video mode? I'm going to Best Buy to pick up the camera, can I get a stabilizer there as well? Links are welcome.

Sorry, I'm just starting out but I want to be able to take decent videos with the amount of that jello-y effect as possible. :]

Added (1). ALSO - People keep saying there are ways to fix the rolling shutter issue that those with video DSLRs have been using for a while now. Can anyone explain how this is done / the post-processing aspect of it?

Stabilizer? I don't know from a stabilizer. A tripod perhaps? The camera will have vibration reduction built in but that for stills. What is a stabilizer in this context?

I'm equally lost. If your main interest is taking videos, why don't you get a "real" digital video camera instead. The D3100 is mainly for still shots. The video, as you already know, is just a minor feature.