My mother-in-law tells me that part of the handle on her outside faucet broke off. She says it hurts her hand now to turn the hose on or off (she's 84.) Can I just replace the handle or does the whole faucet need replaced? If I try to replace the handle, do I need to turn off the water inside first?
No need to shut off the water. Just remove the screw holding the handle on and pull it off.
Your going to need to take it off before buying a new one. Some are square, some are splined and you need to know which one it is.