I have a dent in the left rear of the box of the truck. It is about foot and half from the tailgate. I tried the plumbers helper the plunger. It didn’t even move it.
Depending how deep the dent is, this might work. http://www.youtube.com/watch?v=ILVWPzO_swY
If there’s no paint damage or creasing, check into one of those paintless dent repair places. I’ve been very satisfied with their results in the past.
I saw another video like that, except a small block of CO2 (GLOVES, PLEASE!) was used to cool the dent.