How do I fix a mini-fridge fan?

I purchased a mini-fridge about a year and a half ago and 6 months after I bought it, it stopped getting cold. I recently discovered that one of the fans was no longer working. Does anyone know why this could have happened or how I can fix it myself? Any answers or links to instructions are greatly appreciated. Thanks!

Take off the back panel to access the fan, the new one screws in place.

1975 Chadwick-Miller Mini Fan.