2008 Mazda 5 alternator replacement; how much work does this involve?

[aviphysics]

My wife's alternator has excess ripple, according to the machine at the auto parts store. I am guessing that either the belt needs tensioning or the alternator needs replacement and my bet is on the latter (unless someone who knows better suggests otherwise).

I think I would like to replace the alternator myself, but I am hoping I can get a gauge from someone here of what is involved before I get started.