If you can remove any interior panels to access the dent from the inside, you can then place a small 2x4 piece of wood (on the inside) and hit it with a hammer to push it out.
If you cannot access it from inside, drill holes in the center of the crease and use a
slide-hammer to pull the dent.
Cheapest route for DIY:
After repairing, grind the area smooth and remove the paint from the affected area(s), fill the holes with bodyfiller, let dry, sand with 220 grit to get smooth, use progressively smoother sandpapers up to 500 grit, finish wetsanding with 600 grit, then paint.
Redneck route:
Apply filler, silicone, or bubble gum into the hole... call it a day