Check with whoever did the oil change, and find out exactly what brand of oil they used and type of filter (paper or fleece.. fleece is recommended). Was it Synthetic or regular oil? And like Larry said the oil should be labeled to meet Mercedes specification (229.5). Then let us know. Some synthetics might be ok, but mobil1 would be brand of choice. The reason is that our engines are engineered to use particular oil lubrication determined by Mercedes to be used. Depending on your average climate temps, you might be OK.
IMHO if you had the oil change done at one of the quick in, quick out places, for $26.95, I'd be concerned. This is why many of us do our own oil changes, or bring Mobil1 0-40 and a Mann fleece filter to the mechanic.