92 running hot, loses power, codes 21, 52

1992 Cherokee with 68,000 miles. Running really hot and no power especially with ac on and going up inclines.
Can't believe the guy at the garage today says he drove it several times and couldn't find anything wrong!! Picked it up and drove it 3 miles and was so hot I couldn't touch the oil dipstick! No check engine light comes on though.
Got a code 21 and 52 when counting the check engine flashing after reading online how to do it. Code 21 is 02 sensor and Code 52 is 02 detects rich mixture.
Could it be the catalytic convertor and how does this tie in with the 02 sensor. Crawled underneath and cat. looks rusty and little pieces chipping off. Just had a new muffler put on by Midas two weeks ago and they didn't see this!!!???
Does anyone have a good garage I can bring this to!!!
Input please.

Change the O2 sensor it controls the mixture. It is as easy as changing spark plugs. It cost about $50 for the part.

Zhanks is right. There are numerous posts on some forums here where the O2 sensor failed, and the mileage went way down. The O2 code you're getting, plus the rich mixture, indicates you might have the same problem. Is the inside of your tailpipe black and wet? Getting worse mileage? If so, sounds like an O2 sensor replacement is in your future.

However, this by itself wouldn't make the vehicle overheat. I'm thinking that you probably have some flow issues with the radiator. If you take off the cap (when cold) I bet you'll see some buildup inside. A radiator shop will often flow test your radiator for you, but I'd think that after 13 years it might be time for a new one.

Once you've addressed these 2 issues, you'll probably be good to go.