If the car has been sitting for four months, go through the standard "service" as follows:
-New battery
-New fluids and filters (engine oil, gearbox oil, coolant, brake fluid, differential oil)
-New glow plugs
-New belts
-Valve adjustment
-Perhaps new water pump and thermostat
I always recommend buying these kinds of service parts through your local MB dealer, because you know they will be of the highest quality. Don't let $400 or so worth of parts and fluids get you down, at least it'll all be done in one shot and you won't have to worry about any of these items for a while down the road.
Use a good 10W-40 oil such as Castrol GTX and buy one or two extra quarts in case she's an oil drunk
**I might also add that it would be wise indeed to run a bottle of Red Line 85+ or Diesel Fuel Catalyst through the fuel system (just pour into the tank). You can get that here through Fast Lane. 85+ and Diesel Fuel Catalyst are one and the same product, the name just changed and I don't know whether or not Fast Lane sells it as 85+ or DFC.