Common problem. The extruder motor is a press fit (Some are glued) into the cast aluminium housing of the extruder body. What has happened is your motor has slid backward, and that has allowed the gear (which slips over the motor shaft) and bearing to also slide backward.

You'll need to remove the extruder, press it all back together and either glue the motor in place or strap it somehow with a piece of thin wire.

I see someone replied already to your thread though on the M3D forum with the links to the how-to articles.