Do a search on 300E (and W124) and you will get a plethora of threads on the 300E.
This will point you to what to expect as you put miles on your new (used) vehicle.
BTW, oil on or near the front of the engine is indicative of a leaky camshaft cover seal...typically, head gasket failures start at the rear of the motor.
With 200K miles on the car, buy a manual, CD or whatever and learn, learn, learn, this car. Parts costs for this car aren't too bad, and much of the work can be done by yourself if you are patient...having a spare vehicle to drive while servicing is helpful...you don't want to rush a repair job on an MB in the Friday-night-through-Sunday-night fashion.
But mostly, change fluids religiously. These cars are solid, and will serve you well if you don't neglect basic maintenance.
