Timing Chain

[euronatura]

Dear Tech Help:

I have a 1988, 190e, 2.3L, 4 Cyl, auto trans. Benz. It currently has 150K miles on it. I have had the car for 10 years and purchased it with only 50K on it (while I lived in the States - moved here due to work, brought the vehicle with me.) I live in the tropics (Central America) but at 5,380 feet above sea level. Only rains from May to October. Yearly average temperature is a nice 72 degrees (never fluctuates nore than 8 degrees.)

My question is at what point should I have the Timing Chain replaced on this vehicle? Also, if there are any other maintanance issues that I should attack given the millage on the vehicle.

The problem I have here, is that the mechanics do not like doing preventive maintance. Their philosophy is "if it ain't broke don't fix it." But I feel that given the millage, there has to be some preventive maintance that needs to be done.

Thanks in advance for any insight and recomendations.

Ig

P.S. What are the valve stems? have read other posts and seen recomendations on this? Can not find this topic in my trusty Haynes Manuel.