LMFAO AT THAT QUOTE
Find another shop man. So they are certain that ALL 4 of your shocks/struts are blown, as well as out of the entire front and rear suspension that only 2 (out of 8) control arms and 2 (out of 4) ball joints on the front/rear are needing replaced? And, your steering rack needs to be replaced?
Find a BMW specialized indy man, the quote is hilarious. If you are looking for an excuse to lower it then I'm sure you could do so with a Bilstein shock/H&R spring combo quite easily, but for the shaking, you need to replace suspension parts. The shocks/struts/springs IMO are not contributing to the shake, and the shop is trying to take your wallet for a ride.
Start with getting this kit, and getting it installed, cost is less than just the 2 ball joints and 2 control arms they quoted you LOL, and I can probably guarantee that this would resolve 90% of the vibrations. Even without touching your shocks/struts.
https://www.fcpeuro.com/#/products/b...bmw5x10piece-l
Also, I highly doubt your rack needs replacing, you probably just have a leak from the high pressure hoses if anything.