http://good-times.webshots.com/album/562588622NDAfkFThe proper method of dent removal.
If you dont have backside access the best thing to do is get a stud gun which welds a small nail to the dent and allows you to pull the dent out.
I certainly would NOT drill holes in the dents or cut it out and replace with a undamaged piece of metal.
Why would you cut out a dent and weld in a new piece? Now you have to deal with the warpage from welding, plus the corrosive hot spot on the backside of the metal.
With a stud gun and a body hammer you should be able to darn near fully remove the damage. Weld a stud to the dent and apply light pulling pressure while tapping the surrounding high spot with a hammer. This surrounding high spot is the reason your dent is there, its holding the dent in place with tension. Slight upward pressure on the dent and tapping with the hammer on the high will relieve the tension and allow the metal to return to its natural state.
Start welding the studs to the shallower portions of the dent first working towards the deeper areas. DO NOT start in the deep area first, this will cause additional creases within the dent!!!!
Start on the outside and work inward towards the deeper regions of the crease.
You also do NOT need to melt the stud to metal, just enough of trigger pull to get the stud to stick. Any time to heat metal you shrink it, by melting the stud to the dent and having a huge blue spot surrounding the stud just caused a huge shrunken spot and in return harder to repair.