Jivesh,

For most of us on this forum the valve adjustment is a DIY task, but some guys work in shops and can give a quote. I would guess between $100 and $150, as it takes about an hour and I replace the valve cover gasket when I do it. I also clean a lot of stuff and check throttle linkage parts (they have to be disassembled so cleaning and checking them out before putting the stuff back together is not really a big deal but it takes some time), make an effort to have new rubber parts on hand to change the breather hose connection or oil cap if they were leaking, etc. If you have gone over 160K miles without a valve adjustment, I am amazed the car runs at all. I would suspect they are very tight, if not in a zero clearance condition.

Get the valves adjusted, then look at other solutions. Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)