Johnson Chan, how many miles did your Mercedes have when you purchased it? If you've spent $20,000 over the course of 290,000 miles that doesn't seem too bad. If you've spent $20,000 over the course of 20,000 miles that could be quite a problem.
I'm having the car checked out by my mechanic on Wednesday. I will make my final decision regarding the purchase then.
1976 300D (W115) - 330K and still going (sort of)
1991 300D 2.5 Turbo - Sold at 221K
1983 280SEL - Sold at 206K
1981 300SD - Sold at 232K