AS Toro said, see if it's locked up. Once sparkplugs are out it should be fairly easy to turn over buy the crankshaft PTO pulley behind the grille.
Something to check... "crosses" in the engine-to-hydro driveshafts are known to wear out/fall apart/trash themselves. Something MAY have fallen apart there.
If the engine is free and he driveshaft is OK, pulling the engine to get at the starter is NOT as bad as you may think.
Just LOTS of little details!