If bent bumper up on truck trying to pull up a tree stump, how can tell how serious a repair it will be?
Do not use the bumper to pull things with like that, it is not made for it. Depending on the vehicle now a days, you may not have a point that can be hooked to that is safe. Use to be OK to tie directly to the frame, used to be places to do that. I have no idea if they all have them now with the way some of these things are built.
you'll find that the bumper is impossible to "push back down" -- that thing is steel. what I'd do is live with the problem as is. Replacing the entire bumper will cost hundreds. another [remote] possible is remove the bumper and try to straighten it, using the truck's weight on a 2.12 ramp to apply pressure. This is quite tricky as the bumper will try to turn in place, rather than bend and holding it in the right attitude is difficult. back in the old days, we'd go visit our friend who worked at the local frame straightening shop -- their machinery might be able to pull the bumper back into near the correct shape [and it would be a cheap fix]. the possible complication is that the bracket which supports the bumper may also be bent -- some of these are replaceable [they include the mini shock absorber], others are part of the frame itself and nothing short of the frame straightening shop will fix it.