Checking the chain is a simple procedure, and replacing only the chain is not $350 worth. Replacing the rails and other associated components is a bigger deal.
Simply remove the valve cover and turn the engine (clockwise only) to TDC, check to see if the cam alignment marks line up. If you do not see the camshaft mark, rotate the crankshaft one more revolution to TDC. If the camshaft marks are more than a couple of degrees late in aligning, you should consider replacing the chain.
If the engine has had thorough and frequent oil changes, it should not be stretched at all.
'01 C Class, Six Speed
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