I Don't own one of those cars and know very little about them mechanically. I'm not a tech or anything like that, so I'm only going to post my opinion on it.
It sounds like a great buy. With Full service history, The 109k miles is not really high miles for a benz. But it is high for the year. If you consider an average of 12k per year or even 15k per year, it should still only be 50-75k miles by now, maybe give or take a little. But if the car has been well maintained, and has had some repairs done to it which were common problems on the cars, I would think it should be very reliable.
If it were me, and it was a car I was looking to buy, I would have it checked out by my mechanic, and if all was good, I would buy it.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.