I've never seen stripped threads on an O2 sensor bung. They're usually really hard metal.
Is this sensor easy to access? On the toughest one I ever faced, I knocked the sensor body off with a hammer and used a 22mm socket with a 4 ft breaker bar. That worked nicely.
If, on the other hand, the sensor is hard to reach and requires a u-joint or a crowfoot, you might be in for a lot more work.
If this is a car that you think you will keep long enough to do this job again, get an M18-1.5 tap to clean out the threads before installing the new one. Don't forget the anti-seize if the new sensor doesn't already have it.