Why do you feel it needs an overhaul?
1. Is it lacking power?
2. Is it buning or leaking oil?
3. Is the engine starting easily down to 25 degrees F?
4. Do you hear a rattle when after the car fires?
If you answered no to all these questions rest assured you benz is a stong runner!
You can check the slack on the timing belt to see if it needs changed. With your mileage i would strongly recommend it. Mine has 188K and has the orginal. Its not that expensive of a job less than $350 i am told.
Just my $0.02.