Carolyn,
The stem can be removed from the outside, and the rubber seal checked for wear. I use pliers and unthread the part behind the "bonnet" nut that is right behind the handle.
If you replace the entire faucet, you may need to cut into an inner wall.

: Help! Both my outside faucets are leaking, and not just little drips either. We have been unable to get the old faucets off to replace them. I know they unscrew because the back one we just replaced last year, and yes it is already leaking!