That auto body nail gun is a great tool. I have one just like it. I've found that more nails are better than less. There's a trick to it but after a dent or two you get pretty good at it.
As far as the pipe bender goes, if it's the type that goes in the press it will work better on thick material and probably just smash exhaust tubing. I have a mandral bender and it still likes thicker material.I'd be interested in seeing the bender, especialy if it works on the exhaust?