Well, then you have two options...
1. Be the first to do a write up yourself
2. head on over to roadfly.com or bimmerboard.com (both sites require free registration) and ask 'highline' about it.
I've looked too for an "input" seal and have found only references to an "output" seal on the diff...maybe it's not a common fault?
If you go to
http://www.bmwfans.info and look up your car under original parts (you can enter the last 7 digits of your VIN to look up parts, should be under group 33) and tell me what the part number is so I can see what you are talking about cuz I'm interested.
I'll admit, my knowledge only goes so far. Sorry I couldn't be more helpful.
Thanks...