How hard is it to change the oxygen sensors on a 2000 Honda Civic EX?

Replacing O2 Sensors

It is pretty easy if you are handy. It is located in the exhaust manifold.

There are two sensors. one is on the exhaust manifold and the other is under the car before the catalytic converter. i assume you are getting a check engine light if you have a bad sensor. take it someplace to have it tested to see which one it is. advance auto did it for me. although both are easily accessible, they can be near impossible sometimes to remove. my upper one on the exhaust manifold was bad. i was unable to get it out. i ended up bying a stainless exhaust manifold on eBay for less or the same it would have cost me to have the old sensor removed. i also bought the sensor on eBay for cheap. do not get bosch sensor. they are notoriously bad. i would suggest that you try using a penetrating oil on the threads for a few days and then try to remove it. i even used a mapp gas torch which you can buy at home depot etc on it but i had no luck. the torch however made removal of the manifold very easy causing the bolts to come off while using a foot long extension on my socket wrench. good luck, rob