Based on what I've seen on my old 1989 260E (103 engine) the timing chain and guides should still be in new condition at your mileage.
I never had a problem with a leaking head gasket in 235K, although I had to replace it last summer when the valve guides needed attention. I just hope the replacement head gasket will be as good as the original.
That was the first time I had the valve cover off the car in 11 years of ownership.