you should most likely start by banding ot the dents and cutting a hole. put a piece of flat wood, what ever kind on the back side of the dent and just go to town with the mallet. i recommend a hole saw or jigsaw to cut the hole. personally a jigsaw is easiest if you have a cirlce drwn. they will also come in handy in the future but a hole saw is like a one time use thing
hole saws are a bit expensive. i bought my items yesterday, and when I asked how much an 80mm was, $20, not including the $15 adaptor. If you have a dremel, you can easily do it with the cutting tool. Takes about 15 minutes, and 5 minutes to grind it, 2 minutes to use sand paper and make it smooth.
as for dents, rubber mallets are good but you occasionally miss, and than the shit will hit the roof. use the wood block, and a rubber mallet for best results. don't bang it to hard or you'll get indents.