See if you can just slip the new pulley onto the crankshaft. But first, check for the woodruff key. The key is set into a slot in the crankshaft. It prevents the pulley from spinning around. You can see on the pulley there is a matching slot for the key. If the key is not on the crankshaft, you can buy a replacement key. I can't recall whether on this engine it's possible for the key to drop down behind the timing cover. On some other engines, that can happen. That would not be good. If the key is not in the slot where it belongs, there is some possibility it's behind the timing cover. My suspicion is it dropped down there and the mechanic never knew it when they put the pulley back on. That would explain how the pulley came off. But if the key is still right where it belongs, you're good.