Get yourself a repair manual at ANY auto parts store for your make/model, and it will tell you how to replace it. First, you're going to need to BUY a replacement from a supplier. No idea how much that will run you, but you can shop around.
The repair manual will tell you how to go about changing this thing along with A LOT of other stuff. The other stuff you can ignore for the time being.
How do you change an oxygen sensor in a 2000 olds intrigue?
The same way that you change pretty much any other O2 sensor. You disconnect it from the wiring harness and unscrew it from the exhaust pipe. Then you screw the new one in and plug it into the wiring harness.
In theory it is easy. But sometimes those sensors are difficult to reach because there can be other engine or exhaust components in the way. I am not familiar enough with the Intrigue to give you more specific instructions.
If you know which sensor is bad, then see if you can find it and look at its location. You may be able to reach it without disassembling anything else. If not, then you'll have to figure out which parts are in your way and how to get them out of the way.
If it looks too complex, then you'll either have to purchase a manual (like Haynes or Chilton's) at an auto parts store or from the Internet that explains the procedure, or you'll have to bring it to a mechanic.
Good luck!
