Recommend a flash for event photography (Nikon D3100)?

I have my first wedding to shoot in a month or so, and I'm looking to buy a better flash to attach to my Nikon D3100 for better photos at the dimly lit reception (we all know the nasty pop-up flash simply won't do). I'm no professional and don't know much about flash, and while I learn very quickly, a simpler flash (with automatic settings) would be better for me. It would have to have bounce flash capabilities, and preferably be somewhere under $200. Any other photographers out there have a recommendation for me? Remember, I'm an amateur on a very limited budget. Thanks in advance.

Added (1). It's important that the flash isn't very expensive. I understand I can't always get great equipment for cheap, but money is a huge issue here, so something under $200 is highly preferable.

Added (2). The reviews for the Nikon SB-400 Speedlight Unit seem to be pretty good. Based on the details I've already given, would this be a wise choice as a STARTER flash? I can't afford a flash that I will grow into, so I'm going to have to deal with something cheaper for now. So would this flash be good for shooting the reception?

Yigig7

If you can't afford the SB700 or SB900, the SB400 is lookin' pretty good.

I'd get an SB800 or SB900 flash with some sort of diffusion device, such as a Gary Fong light sphere or a LumiQuest Softbox attachment.

EDIT:

The SB400 is a bit under-powered for shooting an event. As HWTM stated below, you get what you pay for when it comes to flashes, and it's better in the long run to get an adequately powered, good quality speedlight flash. At the very least I'd recommend an SB600 flash for a reception. I understand you're on a budget. If you don't mind getting a used speedlight that's clean and guaranteed to work, you could try KEH.com. They're very reputable.

http://www.keh.com/camera/Nikon-Autofocus-Shoe-Mount-Flashes/1/sku-NA219990711610?r=FE