You're lucky it's all hidden by the bumper if you were to put it back on. Being as there really isn't much to a frame on these cars in the rear, you are in good shape. Take a hammer and beat it back out, take some vice grips and try to straighten out that metal as much as you can. To help you can finish taking off the bumper and compare sides. Get a new taillight and bumper cover and you're in good shape. Be sure to spray black over any areas that will get paint chipped off of them so that it will not rust. Worked in a body shop for 3 years.