I believe an "A" service is just an oil change an fluid top off. I will estiamate

At my dealer 20 years ago it paid 0.6 hr.

Estimate

$80.00 Labor
$100.00 Genuine MB Synthetic Oil
$30.00 to be fleeced for a Fleece oil filter
$20.00 We used to add a bottle of Techron
$10.00 WW fluid and additive
$10.00 Air for tires

$250

It would be interesting to see what the dealer wants today.

John Roncallo