high mileage and what to expect

[Hocky]

My 1997 C180 Euro version has 224,800kms on the clock and the last check showed noisy tensioner in Feb2004. The drive belt also looks like needing a new one, I am not sure. Noises come on when the car is started with rattling noises at about 1200rpm. Takes about 3 minutes before the rpm drops to 850 or so and the noises go away. At idle after this, the noise is gone and only normal sounds. However, when gear is choosen, the noise comes on again and is quite disturbing on the drive. What should I be looking for or listening for when the timing chain is going to fail and about when is this to be expected in terms of mileage expired? Could it be anything else involved like valves or other stuff getting loose with age inside the engine? Otherwise everything works like new, except the trans holds the 1st for a longer period than a Japanese car does, but it does not give the traditional jerk as it changes to the next gear. My 1994 C180 gives me the usual jerk every morning unless I move off at a slow speed and build this up slowly for the engine and trans to warm up. All comments will be accepted, thanks.