1992 300SE - running warm in hot, city driving

[86560SEL]

My uncle has a 1992 300SE with 109K miles. The car runs beautifully- I have driven it. He said when its hot out and when in city driving, that the car will run warmer than it normally did, especially with the A/C on. He bought the car brand nearly new (when it had 7300 miles) and he said it seems to creep up more and more as time goes on. I asked and he said that the mechanic said that the radiator was OK and water pump and that the headgasket was probably wearing out, but not to be concerned now, but to keep a close check on the temperature gauge when in hot weather, which is the norm here in the southeast.

I am wondering, are these engines known for headgasket problems and does it sound like a HG issue. Also, the rear end is floaty. How difficult are the rear struts to change on these cars?

Thanks.