Bring back the leather?
I've had decent luck with SEM products for re-coating the wheel. It is a spray on coating designed for exactly this. You really need to give it some time to cure before using it again so this might be hard if the car is a daily driver. You could let it sit for a day and then for the next week just be very careful with it. Steer using the wood parts of the wheel and not the leather while it cures.


I know of no way to fix the wheel and knob other than recoating. If an available SEM spray-can color will match the seats, that will be the easiest way. I would use lacquer thinner or a similar solvent to remove the present coating, and then apply the SEM coating per their instructions.
Perhaps using a conditioner that doesn't attack the present coating would be the best approach to treating the seat leather.
Nivea cream is the best product that I have found. There are numerous very favorable reports on this and other Mercedes forums, as well as Porsche forums on the Nivea. It is important that you ensure that you get the original German product. The Nivea cream on the US market is not normally made in Germany, and the formulation is different. The German formulation appears to be much better for leather. It is usually available on Amazon.


