I worked in an autoparts store for three years and saw lots and lots of perfectly good alternators getting returned as cores for rebuild. I really think there's little difference between the lifespan of rebuilt alternators. I think the biggest determinant of having a good experience from your alternator is by considering it as a "part" of your battery. A bad battery will kill a good alternator, and a bad alternator will kill a good battery. People get into vicious cycles and have no idea what is happening. Make sure your battery is holding a charge so the alternator doesn't get stressed, and make sure the alternator is putting out the correct voltage and current so battery doesn't get cooked. Unless the bearings or the windings are shot all you'll really need is the regulator. Two screws and you're done. It's not totally obvious how to diagnose a bad alternator. It's easier to diagnose a bad battery - charge it fully, let it sit overnight, and test it with a high-discharge tester (the kind that gets hot and has internal coils). An alternator needs a minimum voltage before it starts to work, so you can't charge a fully dead battery with an alternator...

Replacing an alternator is not all that difficult if you are comfortable with the operation of the serpentine belt. There's tensioner that is tucked away and has a 13mm hex fitting, near where the thermostat lives. Getting to a happy place with the serpentine belt is not effortless the first time you do it (or the second, third, or fourth times for people like me). Otherwise it's 3? bolts to remove the alternator from the housing, plus the wiring.

So to make a short story long, I'd go for the regulator and run a battery test before putting it in. (Also make sure your serpentine belt is tight enough. )That will confirm the diagnosis of a bad alternator and prevent you from killing a new alternator with a bad battery

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