If you're worried, take it to a mechanic and have the chain checked for stretch, otherwise don't sweat it.
Most people get panicky about timing BELTS after being conditioned to big bills every 60k-miles by Honda.
On my 190E's, I would do the chain and tensioner about every 150K-miles, just for peace of mind. At that mileage not one was out of spec. Also, on those 'ol 2.3 8V engines, it's CHEAP. Less than an oil change on an SL600:p
1998 C230 "Black Betty"