I have a 2006 E90 with 95,XXX and I just bought the parts to do it. I would recommend to wait until 90k+ - that is, if you want to keep the car after that mark, otherwise, why bother?
I think that BMW will take care of that if your transmission oil is leaking, and that is very common among E90's. Not sure if they will change the oil just because you feel like asking them to, after all, they recommend this service at the 100k mark.