Would this lens work with my camera?

Http://winnipeg.kijiji.ca/c-buy-and-sell-cameras-camcorders-Sigma-70-300mm-Zoom-Lens-With-Macro-For-Nikon-W0QQAdIdZ423699247
i have the nikon d3100 and shooting a wedding in january will this work and is it worth the price

While that lens may work on your D3100 (if it has an auto-focus motor in the lens), it is NOT the right lens for shooting weddings.

You need something like the new Nikkor AF-S 70-200 mm f/4 lens

If you can't afford the equipment you need to shoot weddings, you need to raise your rates

I have the Tamron equivalent of this lens. They are both low quality lenses (that means cheaply made). You really should have a better lens for the wedding. At a wedding that I attended recently, the photographer used a Nikkor 18-200mm f/3.5-5.6.It may be the least lens you should use.
http://www.nikonusa.com/...VR-II.html

The one thing you'll really need is some form of a flash. The one on the camera is more of an emergency flash. Get one for your hot shoe. I chose to not get a Nikon flash, and got one that has good user reviews off of Amazon. It does an adequate job.