without knowing what previous services had been performed and when, then it is hard to give you a really good answer that will use your money wisely.
If you intend to keep the car for much longer, and want the car in the best shape - then all the fluids should have been changed at some point within the past fifty-thousand miles; transmission fluid, power steering fluid, brake fluid, rear differential fluid, radiator fluid. Of course engine oil at increased intervals.
Brakes should be checked to determine pad and disc life, plus brake lines should be inspected.
Hoses and belts should be investigated to know when the last time they were changed.
Timing chain should be changed only if it had never been. and if this work is done water pump replacement should be considered.
Underside of car inspected for rust, suspension parts should be inspected for play.
Battery fluid level checked, or battery replaced if more than four years old.
Drive train flex disc should be inspected for cracks.
Electrical fuses should be replaced every ten years.
Fuel lines inspected and filter changed.
Hopefully; I gave you some idea on things your money should be put toward. And looking at the above list it is pretty good at listing from most important to least important.
Where ever you take the car make sure it is a Mercedes specialist, and gat a written estimate and only sign it once you review and understand each item. All replaced parts should be asked to be returned to you.
p.s tires, bulbs, windshield wipers, air filters and cabin filters are all things you can install yourself or shop for low prices and installation on your own.