2002 Jeep Grand Cherokee OBD-II P0158

Hi, we just hit 99,000 miles on our 02 Jeep. At 99006, the OBD light came on. I googled and found out that i can find the codes by turning the key (soo cool) the code it told me, was P0158 which i found to be “Oxygen sensor input voltage maintained above normal operating range”. I have searched around and it seems i might have a bad O2 sensor, or a million other things.

Does anyone have any advice, should i try to change the O2 sensor myself and see what happens? Should I go to a mechanic and tell them I already know that its code P0158 and maybe that can same me time/money? Do I need to go to AutoZone and have them test with the device to get more info, or will it just give me the same code?

Should i unplug the battery and try to reset and see if it happens again?

any advice is greatly appreciated!

Car runs OK? Get it cleared see if it comes back,then regroup