Oxygen Sensor Location 2000 Maxima SE

Sorry about this as this information should be available but I can not find it on this news group or elsewhere.

Have 2000 Maxima SE with 'Service Engine Soon' Light; diagnostic check indicated it is:

Bank 2 Sensor 1 oxygen sensor.

I am having extreme difficulty determining if this is:

a) Oxygen sensor in exhaust manifold for even cylinders (2, 4, 6) pre-catalytic converter

or

b) Oxygen sensor located after catalytic converter.

Confusion stems from varying nomenclature regarding bank "x" and sensor "y".

Any help would be significantly appreciated as shop wants ~$275 to replace while I can probably get part for ~$100 and do myself.

Thanks in advance,

Matt