Its really easy.
You will find the top of the shock nuts under the back floor cover.
remove the plastic parts on both sides and you will see two rubber boots
on both sides. The rubber boot closest to the tailgate is the shock .
Remove both the nuts.
Remove the nut and bolt from the bottom of the shock . I didnt even have to raise the X5 to do this .
The shock fits in without any effort if you have the X5 level and not jacked up.

I put a set of Bilstiens in the rear of my X5 and it stop the teader-todder effect.