Broken power button, how to fix?

Hello, My iPhone 3gs power button has suddenley stopped working(I drop my iPhone many times) and i would like help for fixing it. I think the power button needs replace but i don't know how to do it, i know i need to replace the power button,mute button,volume button and headphone socket ribbon but im not sure how i do this. Can someone please help me and tell me how to replace the headphone socket ribbon.

Thanks.

I am sorry for my English, i am Portuguese.