If it's brass colored it's the correct post. The bad post is zinc colored (think dull silver, rather than dull gold). It'd be pretty hard to mix them up.

 

Shortly after joining this forum I found out about the aux post, run out to my car to take a look, and see that it had indeed been replaced, most likely because it seems the zinc one at the very least melted through the post plastic cover. It's fun owning a used car!

 

Thanks guys-it does look replaced and now back to the current issue I am tracking down, and can't wait to get the Z28 cluster in soon.