The '83 should be a great year to buy. Lots of time proven components. High dollar thing to check is the climate control. Make sure the A/C is working properly or deduct as much as you can from the price ($500. to $1000.) Pull the trans dip stick,ck the oil color(red) and take some oil and rub it between your fingers and smell it to make sure it doesn't smell burned.When driving the car, ck for crisp, firm shifts. These transmissions can have a bit of "flair" when shifting from second to third. The CD's can leak through the side window glass. Ck how the front and rear side glass come together at the seal.
Before I EVER start a car I am looking at, I check the engine oil level. It will be black but I want it at the full mark.
Look at the lower front ball joints and see if the grease boots are torn or missing. Ck the tie rods for the same. The ball joints aren't easy for a "Do-it-yourselfer"
If you feel unsure about inspecting the car, The BEST money you will spend will be having a mechanic or Mercedes specialist inspect the car BEFORE you buy

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.