Have you searched for a Xbox library yet?
How do I convert the signal from the xbox reciever through the laptop to arduino outputs through the Xbee
3:How do I map the buttons to control the servo I want it to?
usually the library comes with a button test,it may say button A was pressed, Dpad left is held, it may give you readings of the analog sticks, etc. You just have to look around. There is a video on youtube of a guy controlling a RC car with a Xbox controller, did you watch that yet? Maybe there is a link as to where he gotthe code.