Check out the posting on disintegrating harmonic balancers, I believe all the info you need is there. I do not know if they are one piece or two piece myself -- if they are like the older ones, you can unbolt the balancer from the hub and don't need to remove the nut.

The weight of the car will be sufficient to return it to level (or you can use a floor jack to lift the control arm. If on jack stands, be carefull, you do NOT want extra weight in the trunk or it may tip up and roll of the jackstands.

You have four O2 sensors because these cars use one before and one after the catalyst, and you have a duel exhaust up there. Each bank is individually controlled. Overkill as far as I'm concerned, but you cannot do anything about it.

An O2 sensor for a Ford Mustang fits the W124 gasoling engines, but I have no idea if it will fit yours, I don't have anything nearly that new!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!