Hi Pat! Copper wort chillers are pretty easy to maintain overall, and they do naturally get a dull patina on them that will go away by dropping it in some boiling water (or wort). Where you need to be careful with an older copper chiller is that they can develop something called verdigris, which is toxic. Verdigris is a blue/green buildup on the copper like what makes the Statue of Liberty green. If you see any blue/green buildup or even black (which is probably just heavy oxidation of the copper), use some distilled white vinegar and a rag to remove all of the buildup. After you’re done, I’d throw it in a kettle of boiling water for a few minutes.
Once it’s clean, just make sure you rinse it well after each use and hang it to dry. Never soak a copper chiller overnight as it can accelerate these issues.
Good luck with your new chiller, and thanks for joining BrewTogether! The community on here is awesome and growing every day – they will be a great resource for you as a new brewer!
Cheers!