Situation:  I was leaving CVS on the way home and my Jeep suddenly went from a little loud to LOUD 

  I climbed under it and it looked like the cat had fell onto the skid plate.  I decided to hack the cat off and get a test tube and take it to the local muffler shop to weld it up.  The next time I got a chance to look under the Jeep I realized that it already had a test tube and the test tube had slipped off  

 Also, besides the stock muffler, it has a resonator or small glass pack instead of a tail pipe tip out back 

Quandary:  (1) Should I have the local shop weld the test pipe on and cut the resonator thingy off and replace it with a tip?  Or, (2)  

 Should I have the test pipe fixed and have a turn-down muffler put on that dumps after the skid plate?  Would this rust out my Jeep or cause problems other than a few in cab fumes in the winter?  I have herd yes and no on the rust.  I like loud, but I don't want to mess anything up.