I just installed a bolt on Random Technology SuperStainless Cat a few weeks ago (with a Banks header and a Banks cat back).
The hardest part of the job is the header and the head pipe, so if you're only messing with the exhaust from the cat back, it's all pretty easy.
I definitely recommend the Random Technology cat (unless you live in California).
Christian / Husband / Dad / US Navy Veteran
Current Jeep: 2009 JK UR (3.8L, 4-spd auto)
Previous Jeep (1): 1994 YJ S (2.5L, 5-spd manual)
Previous Jeep (2): 1997 TJ SE (2.5L, 5-spd manual)