Schettini, if you haven't already check the oil level to confirm how much oil discharged from the engine while running without the oil fill cap. I would be more concerned about how much oil discharged from the engine than some dust entering through the open oil fill hole. If the oil level got too low it's possible there is major engine damage. Add oil, as required, so the level is at the midpoint on the dipstick gauge. Did any of the dashboard trouble lights come on while your wife was driving, or did the engine overheat? As for the alternator I would spray it with brake cleaner to clean off as much oil as possible. The engine is likely stalling out because the alternator is not recharging the battery. Consider replacing the voltage regulator which attaches to the back of the alternator with 2 screws, or at least remove it and clean the brushes and the armature. It's possible you will need to disassemble the alternator to clean it properly. Inspect the spark plug recesses to make sure they aren't partially filled with oil, and check that the distributor cap is dry and oil-free. Good luck.

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Fred Hoelzle