The bigger less crinkly dents by the gas door and around the wheel well should be able to get better without too much work, by the tail light is going to be a pain, I knocked a bunch of smaller dents out of my '97 a few years ago with a slide hammer through the tail light hole then some hammer and dolly work, also knocked some dents out of other panels with some hammer and prybar work (all sorts). Depending on your patience level you might be able to get it pretty decent... I tried to look for before and after pics of what I did but I didn't take much as I just got a wild hair one day when I took most of the dents out of the old tailgate after I got rear ended...
Rough body work is a lot easier than you think, just think of what it will take to reverse the force that got it there, on the inside of the bed just reach under with your arm and try to push outward, should get the big ones out, the more dinged the more force will be required and creases are very hard if not impossible to get perfect... by the tail light will most likely take a slide hammer with a hook or the stud welder that was posted above...