I know from experience what it is like to resurect a lifeless beast. I bought my mother-in-law's 85 380SE. After checking the records in the maintenance manual, the best I could estimate is that the car had been driven 3,000 miles in 7 years. I knew that the last couple of years were the least driven ones too. I replaced every fluid and filter in the car. My rough running was due to a bad plug wire tip. Fresh battery, plugs, cap, rotor, and wires had the engine purring like a kitten. The tires had full tread on them and judging by the cracks, they were around 7 years old too. Replaced them and the ride improved. What I have found over the long haul is that anything and everything that is rubber on the car has deteriorated substantially. I have personally replaced every front-end joint except for the upper control ams. I still need to replace the rear bushings, all springs, and the shocks. I keep praying that my cracked looking CV joint boots don't decide to let the magic grease out. It was suggested that I liberally spray silicone oil on those boots at every maintenance opportunity the arose.
Since I now work at home, I am putting about 4,000 miles a year on the car. It is a long time between oil changes. I really need to get a battery charger.