Just a quick guide for this, its dead easy and should takes less than 10 minutes.
This is on a 1990 735i but im sure theyre all the same
Youll need a small flat blade screwdriver or knife and an allen key or allen socket, 10mm i think but the pics show it
So you need to remove your rear bumper
so get your screwdriver/ knife and push down the small tab you see inbetween the chrome and the plastic, theres one each end of the bumper and 2 spaced out evenly nearer the middle
once youve done both sides slide off the chrome trim, shouldnt take much force and should slide back towards you easily
then get your allen key or socket onto here and remove both bolts, one each end of the bumper again
then get you hand on the bumper here and pull it out from the arch and slide the bumper back an inch or 2, then do the same other side
do each side once more till the bumper is resting on these supports and is almost off
get both hands in the gap there and slide the bumper back and off, its not too heavy
when you go to refit it just make sure you slide the tabs over the guides for it thats attached to the car at each side, maybe grease the guides. Check the rubber seal/ trim on the leading edge of the bumper is on properly.
Make sure the arch liners are tucked in behind the lip of the bumper
Do up the 2 allen bolts and then the chrome trim just slides on from the back going towards the front and itll click into the tabs