On a 700/900 it is totally straightforward to pull the brush/regulator assembly-- two phillips screws and you have it in your hand! No need to remove the alternator-- just pull the negative battery cable before you do it. If you have a pick-n-pull near you, you could simply pull out the assembly on a junker and put it in your alternator. I keep a few around as spares. If you want a new one, try online parts places like fcpgroton.com-- even at $35, it is way cheaper than a rebuilt alternator, and likely the only thing wrong with your current alternator-- these units are very robust.

Measure your alternator output at the battery with the car running-- if it is below about 13.7V, just replace the brush/regulator assembly.

Good luck!
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Herb Goltz, Aurora, Ontario, Canada '92 245 w/130K mi, '92 945T w/200K mi