I did this on my car a few months ago but don't remember if the '92 300e's have m103 motors. If they do, all you have to do is unplug the wire, then I think I used a 22mm wrench (same size as the o2 sensor) to loosen it. I did this from below while doing the transmission filter, as I had a rather long wrench and there's not too much room from above. I did the rest by hand from above and let it drop down and went back down under the car to put the new one in. You could probably do it from above, though it might be tight. Good luck!