95 Pontiac Firebird leaking oil and check engine light is on?

I recently bought a 95 Pontiac Firebird and it has been running badly. I changed the spark plugs and the spark plug wires, then the coil packs, it runs a little bit better the Check Engine light is stil on and it is leaking oil in two spots, when you look under the car, one leak is coming from directly under the oil filter, and the other seems to be coming from the pipe that goes to the catalytic converter, or the oil could be dripping onto it perhaps, not sure there. Would a bad catalytic converter cause this? I'm sure that the oil filter needs to be changed but it kinda putt putts...