Jon,
I have done 4 of these repairs. It is fairly easy. I am assuming that you have a new dogleg panel in hand?
Drill out the spot weld along the bottom and seams by the door jam and rocker seam. (use the new parts overlaid on the car to mark out where to cut the old piece out at the top -horizontal cut in the 1/4 panel)....so spot welds are drilled out along the bottom (pinch seam), along the rocker panel seam, along the wheel well pinch seam, and cut (I used a cutting disk) along the horizontal line from the wheel well to the door jam (this is the line that is drwn with a sharpie using the new part overlaid)....cut below the sharpie line, not above---it is easier to trim a bit more off when fitting the new part, than if you have cut too much off.
Now us the old piece that has now been cut off the car to transfer the spot weld hole locations to the new part. Drill holes in the new part in these locations. Fit the new part to the car (trim the cut line if necessary to create a nice snug butt fit). Spot weld at the drilled holes, and stitch weld along the horizontal cut. Use some kitty hair filler at the horizontal weld (grind the welds smooth), sand down, then skim with plastic filler, prime and paint. You can get both sides done in one afternoon.....
Kinda hard to explain by typing....let me know if this makes sense.....
Tim