I bought 10 sets of the outer door handle gaskets from the source in Malaysia (dealer only sells the handle complete with the gasket) for some members of our E32 Club in Japan. Here are the info pics from my friend Mitsu, job done on his 750iL Highline.
Remove the plug in the door, use flashlight to find the slider inside the door, push the slider forward towards front of the car, remove door handle from outside, replace and do same in reverse.
It makes it easier to fit the gaskets snug when you let them warm up a bit in the sunshine or water, so that they are more flexible to install.
Language Japanese, pics international
http://infinitier.ddo.jp/e32/mainte_053.htm