This is a replacement fan the Cabinet Vent (CP-CV) and is easily replaced by simply removing the old fan from the housing and swapping it out with the new fan.  Just for reference, this is a 50mm x 15mm DC Fan with a specialty bearing system that reduces noise and increases longevity.

 

Replacement -  For older mounting system, remove the 4 screws that hold the fan assembly into place and remove the assembly from the housing.  When reinstalling, ensure the fan is positioned where the airflow is in desired direction and there is an arrow on the side of the fan that indicates the direction of the airflow.  Once that is determined, ensure to align the power wire with the notch in the fan bracket and reassemble.  With newer mounting system where the fan is mounted using rubber mounts, simply pull the fan from the mounts by working from one corner and 'releasing' one mount at a time.  Trying to pull the fan straight off may damage the fan mounts.

 

Polarity.  This fan is polarity protected so if polarity is reversed, the fan simply will not operate.  Just reverse polarity ensuring that Tip aligns with + on the ends of the connectors.