I have the 1988 735i and did it the same as rainman except for the following. I did it while it was in the car. I cleaned it, grabed it with both hands, twisted and it came off. Cleaned the area where the new O Ring would seat. Dripped fluid into the new one with a clean squeeze bottle. Twisted it on. TIGHTENED with a chain wrench just tighter than I could by hand. A chain wrench looks like an oil filter wrench with a chain instead of a strap. I have read that Strap wrenches will work too.