Since it seems it was making noise, it's worth replacing. Cheaper than being stranded or having it come apart and damage something more expensive (radiator made of unobtainium for example).

If the bearings were seizing up in the alternator, it's possible for it to set up some pretty severe "flapulations" in your belt if the tensioner shock is worn. If it was doing that, tension in the rest of the system goes slack and you could lose power steering. Just a theory.

You might add tensioner arm, tensioner pulley, spring, and shock to your service list. They frequently fail and can cause all sorts of problems if they're ignored (cracked/broken timing cover, fractured accessory mounts, shredded belt, radiator damage [ remember - made of unobtainium ] ). The parts aren't expensive and they'll get rid of a low "growling" noise if your engine makes it.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]