I'm thinking of buying a 1996 850 GLE from someone I know. Extremely low mileage, 52,000 km. But it's been sitting for three years with half a tank of gas with somebody moving it for a short distance once a year.

I did some visual checking: coolant looks OK; oil is low but no spot of leakage under the engine; p/s and brake fluid at correct level; trans fluid not checked.
Battery probably needs replacing. Expect tires may have a flat spot and will need replacing as well.

I did not test drive it due to insurance issue but did start the engine in the car port it parks. It starts, but stalls on idling. Coolant temp looks OK as it rises up to the mid of the gauge and stays there while I keep the accelerator paddle. I used an additive to help remove any water in tank. At first not much change but next day I started the engine and it seems to run a little better now - if I release the paddle slowly, it stays at about 700rpm on idling and the engine shakes but keeps running. Engine stalls if I let go the paddle faster.

What kind of servicing do I need in addition of fluid changes and other visible issues such as battery, tire etc. Any suggestions on what this car might need after sitting around for so long? Was 1996 a good year for 850's? Any suggestions on common problems to look for with a 1996 850?

Your kind advices are much appreciated.