Jim:
I send all my Shimanos to "Shimano". $35 per reel and they do a complete overhaul. Go to:
Repair Services
you will find a repair form (PDF). Just fill it out and send with $35. They repaired 2, 400s I have. Minor stuff such as the drag slipping and the level wind not working correctly. They went over and above what was needed and replaced some screws, etc.