98 TJ catalytic converter

Hey folks, my little jeep has a cat problem...its rattling around and makin all kindsa racket...had it checked out and, of course, it needs to be replaced...least the guy was cool and said it wasnt immediate and he would drive it till it fell off...(never mind cloggin the cat back stuff) mileage is still what it was when i bought her, no problems otherwise. So what is the best place to buy a catalytic converter? direct-fit a good one? he quoted me 450 bucks and I know i can get it cheaper...can i do it myself? whats the best after market place to get one? i searched around google and see alot of them...thanks for any help...