If it's a circuit breaker mounted in a "power center" panel as shown below, it can be replaced. One would need to first shut off the main breaker, then remove the metal front of the panel, loosen and remove the wire going to the faulty breaker, then unplug the faulty breaker. Plug in the new breaker (of the same type and rating!), attach the wire to the new breaker, making sure it is SECURE, reinstall the metal cover and finally turn on the main breaker and the new breaker. Remember to reset any clocks or devices in the house that might have been disrupted by the power interruption.CAUTION: If you are unfamiliar with electrical work, PLEASE get an electrician or qualified handyman to do the work. There is a potential for serious injury or death if you make a mistake.