Why two radiator fans, and are they difficult to replace?

Lately I've been noticing when my electric radiator fans come on, there is a slightly louder noise than normal. The noise in only when the fans are running. My question is why are there two fans? If one goes out will the car overheat? Are they difficult to replace? When the motor had been turned off and the engine cooled, I spun the fans by hand and the one turns a little harder than the other one. I'm wondering if that could be why it's getting louder, are there bearings in the fan that could be wearing out?? thanks for any help.

You will have to take the front grill and bumper cover off for the AC Fan. One fan is for AC and the other for engines cooling (water). They are not difficult to replace. Just like anything in a small car, a pain for big hands.

Considering we spend a good part of our day idling at stop lights, traffic, whatever you need a fan to blow air across the radiators. And besides with our passion for styling, I am amazed that air flows in anywhere in the engine compartment.