Answers

Talk with your local tree nursery or a state university agricultural extension office.  (Iowa State University has an excellent one.)  I love willows, but if the damage is too severe, you may need to begin again.

I highly recommend getting the opinion of a local arborist.  If you have trouble finding one check with your local tree nursery or Botanical Garden for a referral.  We have used one before and it was the best $100 we could have spend considering the situation.