timing chainer tensioner / catalytic converter

I have a toyota celica gt 2000.170,000 miles. 1st I had the the timing issued taken care of, that was obvious I needed it but does it really take 3 hrs to diagnose? cost $584.87. after driving 50 miles the check engine light came on so back to garage. diagnostic cost $157 problem - catalytic converter & leak in fuel system O rings on hose were leaking. cost to repair $1392.56 now after driving 100 miles the check engine light comes on again. I'm beginning to wonder if I'm being taken for a ride. Guess i'll go back and say the lights on again & what to do? Maybe I'm just upset cause I have to spend so much on my car.