Every alternator I have had sail, failed electrically not mechanically. I have never had an alternator bearing cause any problem. Why would you invest in rebuilding a part for a 10 year old cat that could have countless things happen to it and never need another alternator ?
The bearing noise you are hearing might not be a bearing but an electrical problem in the alternator. That is what happened with my Saturn…The alternator started making a whirring noise. The guy at the generator shop said it was bad diodes.
I think that’s a very good idea. You can have a backup alternator on hand with known good bearings. I had a rebuild shop put new solenoid contacts in my Corolla’s starter motor and all they charged was $10 total. Parts and labor. It took them 10 minutes, and they did it while I waited.
I expect it wouldn’t be overly difficult to install new bearings yourself too. There’s no time hurry so if you mess up you can buy some new bearings and try again. There are probably a slew of utube videos on how to do it. You’ll probably have to secure some bearing pulling tools, but the amount you save by doing it yourself will probably pay for those. Plus you might be able to borrow them from an auto parts store.
I’ll add one caution. Pay some heed to the comments above about getting in over your head on this task and it getting overly expensive. Come up w/a plan to make sure that doesn’t happen. Best of luck. I think it’s good you are willing to give it a go.