Tough questions.
Bilstein recommend different ( shorter shafts )shocks, if you lower much more than 1".
When will your regular shocks be gone.....don't know.
How much will it cost:
1. Springs @ $ 230.00
2. Shocks @ $ 500.00
3. Labour to install & alignment @ $ 300.00.
The satisfaction of not having your car look like a 4 matic............priceless.