http://www.bmwe34.net/e34main/mainte.../o2_sensor.htm
And here my one in Japanese for the E32 750.
http://infinitier.ddo.jp/e32/page/mainte/mainte_056.htm
Also did not drop the exhaust. Just removed the 2 bolts at the rear, then pushed up the middle of the exhaust with a hydraulic jack to get the rubber ring holder form the bracket for the exhaust, removed jack, let the exhaust hang down and then unscrewed it with a normal open wrench. Had no problem, except I mixed up the 2 connectors, and first had the oxy sensors connected across = left side exhaust to right bank and right bank exhaust to let bank. Took me a while that I found out what I did wrong. Engine was running terrible. So had to go again under the car and connect correctly.
For that I recommend to mark the connectors before you remove the oxy sensors to avoid mix up.