I replaced mine in my 95 Bonnie. It is not hard. You can do it from reaching over the rear (between the fire wall and the engine) and using a properly sized wrench. I think I used a large cresent wrench. You may have to break it loose - but mine wasn't hard to do. Are you knibble/flexable:?: You may have to streach a little.

Don't forget to disconnect the wire to the connector. You'll see it.
If you bend over from the drivers side of the car, you should have a pretty clear view of the O2 sensor. It is located not too far down from the exhaust manifold centered on the exhaust pipe. It has one wire coming off the top of it.

Most everyone says to use a O2 sensor made by Delco. Better gas milage. You can ask around and/or search this site to see what others have to say.

Regards,
John