How do I fix the ribbon on my iPhone 3GS?

hi my iphone 3gs power on button is not working though when i press hard on the top right hand side of the screen i can maybe get it working for a second but not long enough to turn the phone on or off though now it is incredibly difficult to even do this and from what i have gathered there is a cable running through the backcase of the iphone which needs to be moved back into place or something so could someone please let me know if this is true and what i have to do exactly as i am a total noob or if something else is the problem. any help would be extremely appreciated.