O2 sensor replacement?

Not sure if this is how to add to a thread/problem?

REPLACED O2 SENSOR (DRIVER'S SIDE, BANK 1, SENSOR 1) - WAS THROWING P1131 AND O2 SENSOR CIRCUIT LOW VOLTS- AFTER PUTTING NEW ONE IN FROM ADVANCE AUTO - CHECK ENGINE LIGHT COMES ON - NOW SAYS P1132 - O2 SENSOR CIRCUIT HIGH VOLTS - CLEARED CODE - RAN AGAIN - SAME THING - could new sensor be bad? Any suggestions? Thanks!

How hard is it to replace O2 sensor (upstream - Bank 1, Sensor1) - Advance auto diagnosed P1131 code as O2 sensor -

It's an '02 Mazda B3000 with 90,000 miles. Bought used and dealer replaced passenger side O2 sensor because truck was idling rough - past inspection and a few weeks later, truck is idling rough again and check engine light came on.

Bought O2 sensor from Advance auto. How hard is it to replace driver's side sensor? Is it easy to get to?

Otherwise, neighbor offered to do it (he is unemployed former mechanic).
He won't quote labor price. What is a fair price to pay him to replace this sensor?

It's not that involved of a job. I'd guess $50-$75 would be fair?
Get under your truck and find the sensor, and see if it's obstructed or easy to reach. Then follow the wiring up and see how obstructed or easy to reach it is on that end.
I don't know your truck, but would I bet you could do it.