Were you hearing any type of noises before this started? Normally, pilot bearings are known for causing grinding when going into gear. But I don't think Nissans have pilot bearings so we can eliminate that. Let's pray like hell that the throwout bearing isn't frozen to the shaft it rides upon. If so, I don't know too many people that will be able to smoothen out the shaft. It will be possible to save it. Can't give you any promises. PM me.