Scanguage indicates trouble w/O2 sensor 1/2 (code P0137).

Question is: 1) best to get OEM replacement or can get other from NAPA; and 2) is this one of those conditions where if one goes bad it's best to go ahead and replace all four?

TIA

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'04 Renny
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Conquests: Poughkeepsie Gulch, Governor's Basin, Black Bear/Imogene/Engineer/Cinnamon pass, Coal Creek OHV, Badlands OHV, S.M.O.R.R., K-Rocks, Parent's driveway