You may be fortunate enough to not have to replace the alternator, but if not, I have replaced mine without too much dismantling.
I got the belt off without messing with the tensioner...I did have to remove the fan for access (3 allen bolts secure it to the clutch). The width of the belt makes install and removal easy. There should be enough slack to pull a bit off near an adjacent pulley, then rotate a free pulley until it works itself off. Did the install in the opposite manner. Hope you have a manual to use as a guide to how it all threads back together!
Two 19mm bolts hold the alternator in place. The bottom on is easy to get to, but the top one requires some effort, as there is little room to move a tool around. This is a knuckle scraping job at this point. I took about 2 evenings to remove the alternator (did the work casually), but it took about 1/2 hour to install everything (alternator, belt, fan) once the alternator showed up at the doorstep.
BTW, your pics show a different unit than the Bosch alternator I obtained. You couldn't replace the regulator as it was internal, so alternator replacement was my only option (Bosch OEM, $160 @ FastLane).
My three-year old battery wasn't damaged by the excess voltage, but I did have to refill a couple of cells with distilled water...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car