If the key does turn out to be sheared and hopefully that is it then it should be good. But I would check for a bent crankshaft on the PTO end before getting to deep into it. These do get bent easily from impact if the impact was sever enough especially when bar blades are used.
And for straightening the crankshaft is usually out of the question on newer engine as the metal is not what it was once. I have heard cases where customers had crankshafts straighten for only it to break off later.
