Unscrew all nine screws. There's no need to remove them. As long as they are completely unscrewed, you can leave them sitting in the plastic, which will make it easier to screw them in later.
Pry open the plastic casing. Gently pry up each corner, being careful not to crack the plastic. You should hear some light pops as each corner unsnaps from the base. Don't force anything. If you meet a lot of resistance, make sure all screws are completely unscrewed.
