mass air flow meter
 

own a 98 c280 from the start. cel light came on at 20k afrer 4 years, did not drive much. guilty of neglect for almost 2 yrs. finally did diagnostics test at
40k the other day, faulty MAF from codes. could this be possible since car shows no symptoms of this. car since new drove like a dream and still does. gas mileage is at 20 /25 city/highway. idle fine, no hesitation. pick up fine. any opinions?

It's still running fine thanks to the adaptation system in the FI. Your system is probably not at max adaptation yet, but has exceeded the threshold to trigger the CEL. Sometime in the near future the AMM will degrade to the point where the adaptation cannot fully compensate and you will experience running problems.

Maf
 

Thanks. I will replace. Where is the MAF located on my c280 and do the codes have to be reset once MAF is replaced or will it reset itself after driving a while.

It's on the intake plumbing. A couple of drive cycles with a new meter should reset the check engine light.