I generally tell people selling a whole working hard drive that's used is often more trouble than it's worth. Simply put a hard drive is a piece of intricate machinery. A single drop or bump could be the end of it. And you'll be dealing with an angry customer on the other end.
If it works First check
amazon trade in. They take quite a few hard drives. It's free, it's easy; and if something goes wrong there's no angry customer reviews to hurt you. Plus if it dies in transit they'll send it back for free. So you can't lose on it.
If it's dead taking it apart will about double to triple your scrap return depending on the drive itself.