need help with 02 sensor 92 skylark 3.3

i checked the diagnostic trouble codes for my check engine light and was given a 44
lean exhaust/ 02 sensor voltage low.
does anyone know if this means i need to replace the 02 sensor, and if so where is it?

The oxygen sensor, or O2 sensor is used to sense the exhaust for a rich or lean condition. The oxygen sensor produces its own voltage ranging from 0 to 1 volt. The computer receives the signal and adjusts injector on time to compensate. Voltage above .450v is rich and voltage below .450v is lean. The sensor should switch regularly above and below .450v. If the oxygen sensor stays below .450v engine is running lean or sensor is bad or shorted to ground. If the oxygen sensor stays above .450v engine is running rich or oxygen sensor is bad or shorted to voltage. The oxygen sensor behind the catalytic converter monitors the converter effectiveness. Because it is burning any excess hydrocarbons it will use up the oxygen in the exhaust making it show higher voltage with less fluctuation then the front oxygen sensor. If the catalytic converter is bad, the rear O2 sensor will fluctuate, the same as the front O2 sensor and set a code for inefficient catalytic converter. Usually, the front 02 sensor is located where the front and rear exhaust manifolds join into one pipe.:uhoh:

so...you think i need to try replacing or looking at the front one,then? or the rear?
i briefly looked under there, and didnt see anything, hopefully i dont have to remove the entire exhaust assembly to get to it, because everything is rusted to crap.
what would make the engine run lean?
what hapenned prior to this was: the car was frozen for 3 days and would not start, it was -17 here. i had only left about 2 gallons of gas in it, and something froze in the fuel lines. i finally got it started by using iso-heat. but thats when i saw the check engine light the first time. i did clear the code by removing the ground on the battery for a few minutes, but now that light comes on everytime the car runs.