You probably have a pretty solid vehicle. The 11’s don’t have timing gear issues like the early M273 engined cars. You also have a revised version of the 722.9 transmission. I would definitely make sure it’s been serviced sometime before. If not, prepare on doing that eventually. Make sure air suspension is fine. You will have issues with it eventually (Airmatic wise) but I feel the pros of the system far outweigh the cons and it’s not too horrible to maintain. Other than that they’re generally solid cars that I think are some of the most beautiful sedans on the road. I wouldn’t worry too much on anything, just take care of the car and you should be okay. Have some money for when something decides it wants to die. Enjoy your beautiful car and have fun. There really isn’t anything like an S. Also, the 5.5 V8 is quite a great motor in my opinion, super smooth but has a deep growl when pushed. It’s definitely enough to make the S550 considered fast imo. 1/2 throttle induction noise is incredible.