It does not sound like a catalytic converter problem would cause all that smoke. Get back to the dealer and explain what you've told us, and I am sure they have your information on file.

A catalytic converter is further down the exhaust system, not right under the hood, and has nothing to do with the radiator's fluids ... And the "fumey" smell could have been that your friend's dad just spilled some antifreeze when he was refilling the reservoir, and they were being burned off when you can the car next.