Open Source I want to take my NAS to the next level

You certainly can. A neater way than using the /dev/disk/by-label/Music path, though, is to use the LABEL option in fstab:

LABEL=Music

Labels, while pretty, aren't as 'safe' as UUIDs, though: if you plug another drive with the label Music in, Interesting Things will happen.

No need to edit the permissions if all you are doing is deleting it:

sudo rm -rf /media/Music/leftoverplexcrap

WARNING: the -rf switch to rm means "recurse subdirectories and force deletion," while "sudo" means "run this command as a different user (and without specifiying the user, as root.)" If you fat-finger the path, it will delete everything from the directory you specified downwards. For example, accidentally typing the following:
sudo rm -rf /media/Music /leftoverplexcrap

Will result in you deleting the entire contents of your Music drive. Accidentally typing this:
sudo rm -rf / media/Music/leftoverplexcrap

Will result in you deleting everything from all currently mounted drives. So, y'know, don't do it. If you want to be sure, replace "f" with "i" to be asked if you really, really want to delete each file, or "I" to be asked if you want to delete groups of three or more files. So, try:

sudo rm -rI /media/Music/leftoverplexcrap

Oh, and a couple of little pro-tips for managing you server more easily. First, have you ever typed a command (like apt-get) without sudo and been given an error? Annoying, isn't it? Sure, you can hit the up-arrow to go back to the last command, home to go to the front of the line, and type "sudo " before hitting enter again - or you can do this:

sudo !!

That will run your last command, but with sudo. Handy!

Remember typing out a long command a while back, but not sure where in your bash history it sits? Don't fancy pressing up a thousand times to find it? Press Control + R, then type whatever part of the command you can remember: bash will search through its command history for matches. Hit Control + R again to search further back if the first hit isn't the one you're after.

Got a long-running foreground process, like copying masses of files from one place to another? You may have noticed that when you disconnect from SSH, the process is killed. Annoying having to keep your desktop switched on and connected while the server's doing something, isn't it? Run the command with "screen" - so, for the copy example, it might be:

screen cp -r /media/Music/* /media/NewMusicDrive/

Everything'll look pretty normal, but if SSH gets disconnected the process will continue running. You can also cleanly disconnect the process from the controlling terminal with Control + A, followed by a lowercase D. This lets you get on with something else while the process runs in the background. When you want to pick it up again, either because you disconnected it yourself or your SSH session was interrupted, just type:

screen -r

If there is more than one active screen session, you'll be prompted. Use labels - see "man screen" for details - to make it clear which process you're running in which screen session.

Finally, if you're thinking about opening SSH to the world so you can fiddle with your server remotely, you'll want to disable root login via SSH, disable password login, set up a public/private key-pair for each of your client systems, and install fail2ban (sudo apt-get install fail2ban) to keep things secure.

Enjoy!

 

Set up a virtual machine on your desktop, install Ubuntu Server, play around to your heart's content until you feel confident enough to do the same on real metal. Bonus: snapshots to easily undo something you did wrong and try again.