I had an O2 go bad and I remember changing it was not a big deal. As another poster mentioned... it is all about figuring out "which" sensor is bad. Research.... I think this site had my answer.
On another note I just started using 93 Octane 100% real gasoline which cost 3.94 a gallon in my 1997 4.3 Blazer and I am getting much better gas milage. It is a breakeven price wise with the 89 fake gas (Ethanol) because of the better milage. My Check Engine light went out. I heard the injectors have a hard time compensating for the lower density of the gas/alchohol/water mix. That is not gasoline! Our Blazers were not designed to use it. Good Luck!

 

wow! I've never heard that side of the gasoline saga before. I've always heard that you're wasting your money using higher octane in a car that doesn't need it. But everything is made cheaper now a days. This Syria thing may be putting my blazer in the garage, while i use public transportation!