The Nissan Path

So I have diagnosed my Wife's noise/power issue and it turns out it is the alternator. But when I go to autozone to look it up, there are 2 available. Which one do I need, or how do I know which one I need without pulling it out of her car, which by the way appears to be no easy task. I would like to know which one I need before I go get the new one, but want to have the new one ready to go in when I pull the old on off. Any suggestion or advice? thanks fellas.

It would help if you provided a year and engine for your Pathy. That said, I don't recommend any aftermarket alternators. For the best reliability, spend a little extra and get a genuine Nissan reman. alternator...or have a reputable auto electric shop rebuild your original.