Pull the end caps off the cover and lift the front panel off the heating unit.
Slide shims between the wall and the back panel of the cover to push the cover away from the wall and expose the screws.
Cut through the screws with a reciprocating saw.
Remove the damper by lifting it straight off the hangers holding it in position. The damper is the movable part near the top of the unit.
Lift the element (the fin-covered pipe) upwards. Pry the bottom of the back cover out of the hanger it's attached to with a screwdriver, then lift the top edge out of the hanger. Do this to each hanger.
Lift the back cover out from between the wall and the heating element.
Vacuum dirt and debris from the fins, and straighten out any bent fins. You can do this with needle-nose pliers, or use a tool specially designed for this task. This will help increase the amount of heat released by the heating element into the room.
Locate and mark the studs along the base of the wall, just above the heating element, with a stud finder.
Slide the new hangers for the new cover between the wall and the heating element. Position the hangers so that they line up with the flat pieces of metal, called the carriers, along the bottom of the fins.
Slide the new back cover plate between the wall and the back of the hangers. Hook the bottom edge of the hangers into the cover plate, then snap the top edge of the hangers into the top of the plate.
Attach the back cover plate to the wall by driving sheetrock screws through the plate and into the studs.
Attach the damper by pressing the clips into position on the hangers.
Slide the end caps over the ends of the heating unit, keeping the flaps open.
Snap the new front plate cover into position, and close the flaps on the end caps to lock the front plate into place.