1992 Chevy Lumina running rough, loosing power, catylitic co

Engine problem
1992 Chevy Lumina V6 Wheel Drive Type unknown Automatic 165000 miles

my car just started running rough and eratic. I see that the catalytic converter is red hot after driving it. I loose power and it has no get up and go at all. It dies sometimes whiles trying to pull out in traffic and it just started having trouble starting. The check engine light has come on and I have had the oil changed and the spark plugs checked, they are fine I was told. What would be the first thing I need to have done to find out what is wrong. I cannot afford much I am a single mom, I do not want to be ripped off. Any suggestions? Sam1967