You only have to straighten the metal tabs that hold the cover to the bottom plate. There's something intimidating about metal fold-over tabs -- they seem so permanent -- but it's easy to undo them. Just worry a small flat blade screwdriver under the tab and pry it up. You can finish straightening them with common pliers.
Those funny looking little nylon snap clips only help to secure the circuit board to the bottom plate, and you don't need to undo them. The screws can also be left in place, as they serve the same purpose.
