He wasn't the only dealer to tell me this tale of woe.  I believe that it's partly because I bought the mower in HD rather than through him.  The common thread in both stories is that in order to become a Briggs dealer they have to stock at least 3 new Briggs engines and a specified amount in parts.  Engine repair warranty claims on Briggs Stratton engines apparently have to be settled by Briggs rather than Toro and Briggs only reimburses authorized repair dealers.  I brought it back to HD and they sent it out to their repair service for a $20 fee.  They will let me know if the repairs needed are covered under warranty.  I ain't holding out much hope.