1996 Ford Taurus Door Lock Troubles

Hi. My daughter's door locks are not working and actually locking on/off on their own. So, we assume we need a new actuator.

So, is this something we can do ourselves? Do you have instructions on how to do ourselves? I think the actuator is about $50. But do I only need one? Is there an actuator in all doors?

Your help is greatly appreciated. Especially since we don't want to pay to repair this right before Christmas.

Thanks so much,
Katie LeMere