Gunk radiator repair?

[Frank Griffin <frankrad4@xxxxxxxx>]

  I have developed a small leak in my radiator, it is at the seam where
the top tank is.  Someone suggested using the some gunk sealer to fix it.
Can it do any harm adding it to my Imps cooling system? If I pull the
radiator and bring it to a shop to be fixed I plan on repainting it
before I put it back in the car. I would like to remove a ding that is on
the top of the tank near the corner. Do they do do that sort of thing at
radiator shops and how much more would it add to the cost of repairing
the seam? 
                                     Frank