Do I need an appointment to take my iMac for trade in?

From the excellent article that hcsitas linked:

You can ask Best Buy, or take advantage of recycling offered by other retailers. Example:

https://www.staples.com/stores/recycling

You can just take in your old one to your local Apple Store for recycling without an appointment.

Maybe not, see Free recycling - Apple. I would call the store or check in person.

Good extra info. :)

That’s me alright 😉

Gotta ask, what happened to your Avatar, BDAqua? I must confess, I don’t have any recollection of it and so don’t miss it…but lots of old timers wanna know 😁. Bring it back, buddy!

No, but you will be required to sign over ownership to Apple while you're there which may take a few minutes.