1991 Accord Alternator Problem

I have a 1991 Honda Accord that still has the original factory alternator in it (173k miles). The charge light came on and I took it to an auto electric shop today and he simply said it needed a new alternator.

How does one know if all one needs is to replace the brushes or if the alternator really does need to be replaced?

Thanks.

So I guess the thing to do at this point is to check the alternator belt tension, or replace your
http://thepartsbin.com/guides/honda/accord/alternator.html (honda accord alternator) belt if it is bad.