Need HELP w/ completing ios 6 update!!!

I updated my iphone 3gs yesterday to ios 6. When it was complete a screen appeared on my phone incidicating the update was complete but just a few more steps needed to be done. I hit the continue button. The next screen indicated I needed to connect my Iphone to Itunes, using a usb cord, which I did. My phone showed up under Devices, and it appeared that it was loading or updating. But then it disappeared and the screen on my phone went black. Now every couple minutes it makes a connection in Itunes, and acts as if it's loading/updaing again, to only disappear when finished.

I am not able to use my Iphone, in any way.

Please, please - help me finish this update so I can just use the phone!!!

Thanks for all, and any suggestions!!! 🙂