How do you replace the alternator on a 1997 Chevy Malibu?

It depends on what model you have, but most are the same.

Disconnect the battery! Loosen the tensioner for the serpentine belt and pull the belt off the alternator pulley. Remove the bolt holding the alternator at the 4:00 o'clock position
Remove the nut at the right rear side of the alternator
Remove the bolt at the next to it nearer you. All bolts have 15mm heads, but you're going to need a deep well socket to get the nut off. Pull out the alternator and remove the plug from it and also remove the red wire attached to the back. You're going to need a 13mm socket and a 13mm flat wrench. Replace the alternator by reversing the steps above. Reattaching the serpentine belt is a pain.