Step 1: Opening the wall wort
I used a chisel to slice the cord at its base, no damage to the case.
As you can see in the photos the chisel is facing away from the plastic so it doesn't gouge it.
Step 2: Prying apart the wall plug
I used a flat head screw driver to pry the case open.
in the photos, i had to use a different plug, the wires leading to the primary coil were melted and not fixable.