Battery light on. How to identify alternator model/brand?

[jac]

I think the alternator or the starter are going bad. I have ruled out the battery as I took the battery to the Batteries Plus and they confirmed it is still good.

I tried viewing the voltage through the cluster but I wasn't able to get to the option.

For now I am just trying to figure out what type of alternator I have to see what the cost of refurbishing it myself or replacing it could be. Is there a way to figure out the model/brand alternator without taking it out? I've had this car for 20 years now but I can't recall if this is the original alternator or not... Lol

Wondering if I should do the oil housing gasket too while I am in there.