[Whaler]

Yes it's as simple as switching the polarity of the wiring. DC motors will reverse rotation when the polarity is swapped.
Now as they say, one must think about that fan blade or taking a fan from the front of a rad to the back or vice versa.
For instance, if a puller becomes a pusher, and you want that fan to stay where it's mounted you must pull the fan blade off and flip it over.
All depends on your application and mount.

Tim