what should I expect to pay when changing the timing belt a on 2002 Mercedes-Benz ML500

Vehicle has 176k miles. Car is due for timing belt replacement. What other parts you recommend changing when timing belt is changed out and cost I expect to pay?

1 answer 2 comments
IT HAS A CHAIN NOT BELT APPROX COST LIKE 3500.00 TO 4000.00
Does this have to be replaced when reaching specific amount of mileage?
whenever they wear out is the time no telling when