The easiest way to replace this is to take the front bumper off and is kind of a 2 person job. Sounds like a hefty task, but it's really not that bad. The bumper is held on by push clips and I believe 2 screws. The screws can be accessed by going to the rear corner of the bumper, by the fender liner. The tires may need to be turned in to get a good grip on the screws with a phillips head screw driver.
The push clips are on top and bottom of the bumper. If I'm not mistaken the top plastic piece that covers the radiator, that is also held on by push clips, needs to be removed to access a clip or 2 located underneath the cover.
Once the clips and screws are off, the bumper is only held on by retaining tabs around the headlights. Now this is where the 2nd person comes in. To take the bumper the rest of the way off, you'll need to start at the corners where the screws were taken off and give a decent pull on the bumper to remove it from the retaining tabs. Remove each corner first, then pull the bumper toward the front of the car.
After the bumper is removed, the resonator box can be taken out. It should be held in with 3 10mm bolts. After it has been replaced, everything is installed in reverse order.
Hope this helps!