I need to repack a 813-3601 Supertrapp muffler. There aren't any button screws holding together and there aren't any rivets other than one under the clamp at the inlet end. In order to take this thing apart do I drill out the one rivet and then broom handle it out or should it come apart with out drilling out the rivet? If I drill the rivet do I need to replace it and if so with what?