Sensors, ??

I have a '97 Sierra, 5.7 L, 4X4. SES light on. Had code read at an auto parts store. Their analyzer said the problem was "Bank 1, Sensor 2". Unfortunately, they had no idea which sensor that is. Anyone know which one it is?
Is it difficult to replace?

ho2s, heated oxygen sensor on drivers side of converter y pipe after converter.

usually not difficult inless rusted into pipe.

Thanks, appreciate the help.