i prefer to bring my own parts to an exhaust shop because they usually put the cheapest part possible and charge premium prices. i buy my parts from rockauto
i got both of the cats replaced for $310 bucks. the first place i went to was a reputable place but they never worked on a patthy before , they pretty much wanted to charge me some computer generated price. they wanted to charge me to get experience on a pathfinder. the second place i went to did not have to remove exhaust manifold and they were done in less than two hours.
i tried the spark plug fouler trick but it only worked on one side because the resonator connected to the cat was broken/fouled up.....
the shop charged me $50 bucks to replace the resonator with straight pipe. i cannot tell the difference because the engine fan is so loud LOL