If the bumper is on the car, you can install/replace the hoses and actuators by removing the valance panel.
The door pivot mechanism, the main mounting brackets (outer and inner brackets) and all the stops and bushings have to be installed before the bumper is installed to the car.
The good news is that removing the bumper is pretty easy...but that thing is heavy. I've done it by myself, but it's best to have a helper. After removing the lower valance and disconnecting the vacuum and electrical connections, there are 4 bolts attaching the bumper mounting brackets to the frame horns and 2 upper retainer bolts at the outboard corners (just loosen these 2; you don't need to remove them completely).
1968 Pontiac GTO
1983 Pontiac Bonneville (G) wagon
2008 Pontiac G8 base