replacing the rear brake shield/dust cover

does anyone know how to replace the brake shield/ dust cover on the rear axle of a 2000 sierra 4x4?

The axles must be removed to do this, including caliper, rotor of course. This may avoided as Dorman makes a 2 piece backing plate for these trucks, check Napa or Carquest stores.

i have already removed all the brake parts and bolts that are on it but it mounts behind a square piece of metal that the parking brake bolts to. how do i take it off from here? i have already purchased the factory parts from the dealer.