Windshield wiper problems 825i

Here's the problem. The motor works, turns, not weak, not slow. The blade does not move. It seems as though the ball joint/socket that connects the blade arm to the motor shaft is stripped.
Anyone else experience this?
Can someone let me know how to take the arm off the shaft?
Can the arm be bought as a separate item, or do I need to buy a whole new motor?

Oh, and this started about 6 weeks out of warranty.