yep, joe's got it right...I just replaced one on a buddy's '89 560 about 4 months or so ago and its pretty easy. You'll need a 10mm (or it might be 12mm-trying to remember) to remove the false wall under the carpeting mat on the passenger side and you'll see it to your left in the footwell area. Just unplug and push the rubber grommet thru. Getting the new rubber grommet thru the access hole is probably the only b-tch part about replacing it because of its "newness" so just put the new O2 rubber grommet in some hot water and it should soften up enough to work into the hole ** (I later ended up using some K-Y lubricant when we did my 560 2 weeks ago which worked like a charm believe it or not-worked better than the water and was quicker!)
You'll also need a 22mm open/box combo wrench to remove the sensor,13mm to slightly loosen the tranny bolts enough to free the wire from the heatsheild, and if you have to loosen your crossmember, there's 6 bolts and they take a 17mm (although I didn't have to do the crossmember thing that some would probably recommend--I just manuevered to get to the sensor). The rest is pretty much a no brainer as you will see when you get into doing the job. Took me just a bit over 2 hours ( with b.s.ing around in the garage and in and out of the house "snacking"). You should be fine. Good Luck and keep us informed.
1970 250C SOLD
1971 250C SOLD