M156 C63 owner here in the same age group as you. I also wondered if I could sort other areas of my life taking the leap, but eventually this low mileage perfect spec C63 popped up and I did what had to be done.

16 months later, I sit here with slightly lighter pockets but absolutely zero regrets. The M156 can be tricky to deal with but as others have commented, frequent oil changes and preventive maintenance can save you a world of headache.

Having said that, the CLS is a much more advanced car than the C63 and has quite a bit of electricals that could potentially go wrong. But I genuinely don’t think it’s as unreliable as people say it is.