GMC C1500 Oxygen Sensor Replace/Remove

I Have Had My Mechanic Change O2 Sensors, Both, And Even The Wires. After A Week, The Engine Light Still Comes On, With A Dignoistic Read...

I Was Trying To Change Out My O2 Sensors And The Plugs Were Different. What Can You Tell Me About This. My Truck Has 2- 4 Prong O2 Sensors...

I'm Wondering If I Can Get Away With Only Replacing The Upstream Or Pre-cat Sensors. My Suburban Has 4, And Is Not Experiencing Any...