No need to remove the fender- - - -the bed makes a better holding fixture than anything you can cobble up on a workbench. Use a body hammer with a little bit of crown to the face, and a heavy dolly on the outside of the metal. Work the dent out a little at a time, starting at the edges and moving toward the middle. If you use the porto-power at all, don't overdo it- - - -once the metal is stretched you'll have several times the work involved to get it right. Don't pound directly on the dolly- - -keep the hammer strokes slightly off to the edge so the metal isn't sandwiched between the hammer and the dolly. You should be able to get the contour within 1/8" or less of the original shape before using any body filler at all, and much closer than that if you're willing to file and metal-finish the repair. Spray a very thin "guide coat" of primer to identify the low spots that need to be raised slightly during the metal finishing step.
Jerry
