As far as the head gasket and the wiring, don't worry about it. It is one of those things that makes you mad when it happens but after you get the car repaired, it is still one of the best. At least you know the weakness before you buy. All in all, I really like driving this car!
And David, I was referring to the 300 sedans when I said 93 was the first year of the 104. Actually, didn't the 300SL and the 300CE have a 104 engine in 90 in the USA? In the USA anyway, I think the 104 went through the end of the C280s as the last model to have a 104. It was a 2.8 as well. I do not know why but the horsepower for the 2.8 is one or two different for the different models and years. My owner's manual says 194 hp for the 93 300E2.8.