In addition to the points made by Niel, you might want to consider using Sync (synchronise) to manage your iPod, something that can be a much easier process than manually dragging and dropping songs onto the iPod.
Ah but, you say; I don't have enough storage space on the iPod for all my music. That's not a problem.
If you use Sync Selected playlists, artists, albums and genres, it allows you to choose what to add and what not to add to the iPod. In other words, you make the choices and iTunes does the work of managing it on the iPod. It becomes a simple procedure to deselect an album (so it gets removed at the next Sync) and then select a different album to be added at that Sync. Much easier than finding the album on the iPod (via iTunes or Finder) and manually removing it.
If you want help with using Sync, please ask.
I agree with Niel by the way, there is no waiting period before you can add music purchased from the iTunes Store to your iPod. You buy the song/album and download it onto your computer:
- if you're using iTunes, it gets added to iTunes and then use Sync to add it to the iPod
- if you're using Finder (on a MAC) the procedure is similar, although I can't be specific as I use iTunes
You refer to "a classic". Remember that Apple made an iPod called the iPod Classic, but it's a very different iPod to an iPod Touch. If you refer to a Classic when you mean an iPod Touch, you will get the wrong information. Consider the point that Niel has made about Apple Music (the subscription service) and the Classic (it's not possible to put that music onto an iPod Classic).