If you are just meaning to swap your bumper for the Envoy bumper then No and No. If you are talking fenders and supports and the impact bar and what ever else then I have no idea?
Do you mean on the sides of the bumper? If so they are big pins that the bumper slides on to, and they lock the sides into place. Just pull it off, and push the new 1 on. Look on the inside of the Envoy bumper at the slots if it isn't on already.
The air bag sensors are on the bottom of the core support. to take the core support off you have to unplug the sensors and that means disconnecting the battery.