replacing rear self levelling shocks

[Curtis]

HI

my rear shocks on my a8 have been dead for a while making the back bounce and i have finally decided to tackle the problem. i bought a set of bilstein HD's for the rear and i am looking for the bump stops and dust covers for them so i can fit them on. does anyone know where i can get the dust covers,bump stops from or can i use audi parts? i cant take them off the old ones because the old hydraulic ones don't have the parts i need.
also has anyone done this before or have any experience they can share to help me with the change over.i heard that the springs will need to be changed as the are lower than standard ones.
any help will be greatly appreciated