If the oil is old then change the oil. I would drain the fuel and put in fresh with stabilizer. It doesn't have to be a lot of fuel. Run the engine with the new fuel until the exhaust is hot all the way to the tips. Pour a little ATF down the carb then kill the engine immediately. Put a plastic bag over the carb inlet and replace the air cleaner. If you don't have full exhaust then put baggies over the outlets. If the engine and fuel system are both well sealed you can leave it sit like this for a few years with no problems. Longer if you completely drain and seal the fuel system. The engine will be protected from corrosion by the ATF and by excluding moisture.