Yes, a wired xbox 360 controller can be used on a PC as a gamepad.
There is two USB slots on the front of the xbox 360 behind the flap plug the usb wired controller into there
Yes you can can buy them.
No
yes - install microsoft driver for xbox 360 and should work with all wired controllers.
You need to buy a PC Xbox 360 controller.
40$
I don't think so
ebay or Amazon
You either buy a new xbox or a new controller.
There are both wired controllers and wireless controllers. The wireless controllers allow you to be farther away from the Xbox and they also have a dock for recharging your batteries.
If you are meaning the controller then yes.