Not kit car related. Can anyone help with any technical information on rebuilding one of these, from everything I've read this is a common problem. I have purchased the bearing and seal kit. It looks fairly straight forward but are there any issues to look out for and how do you set up the pinion/crush washer/nut. Thanks in advanced for any replies.

I used to be part of the bimmerforums. Probably another good place to sign up and ask for help.
Majority of the members are BMW techs, they maybe able to help.

Noted that you've already bought a kit of parts, but sometimes an exchange part can be cheaper and more reliable overall. Might be worth checking what's available out there before you start dismantling it!

An update I took it to a gearbox specialist recommended by a few of my mechanic mates, got the bearings off eBay £150, he found something wrong with the planet gears that he said wouldn't matter if selling car but if keeping he recommended doing it so had that done as well. The pinion bearing was shot, So total £150 bearings £140 labour and £120 planet gears still cheaper than a second hand one and totally rebuilt.