It's not hard at all
-Take out the screws along the wheel wells
-Inside the trunk, there will be I think 2 nuts on either side, and then about 5 or so along the back of the car. I believe you will also have to take out the tail lights to be able to slide the bumper cover off.
-Now go under the back of the car. There will be a bunch of plastic clips along the bottom of the bumper cover. Use a vice-grips to pull the center of them out, and then the outer part will come out easily.
That should be it. Just pull out the sides and then slide the whole thing back. To put it back on reverse the procedure.