Well, you have a few options for your alternator, get a new one, get a rebuilt one, get a used one, or get yours rebuilt, in order of cost.
A new one and usually a rebuilt one will have a warrenty of some kind. A used one won't (for more then a few days).
If you plan on keeping the car for a while, get a new one. If you're a little strapped for cash get a rebuilt one, or get yours rebuilt. If you're selling the car soon and don't care, get a used one.
"Driving is like a narcotic, an addiction that can take over lives. It ruins people, breaks families apart, and even kills. Itís habit that needs to be fueled. Time, money, rationality, sweat, knuckle skin, and anyone who disapproves are of little importance to a driver, and are often overlooked. Hi, Iím Nelson, and Iím a drivaholic."