The slot is for an additional memory card. The 8GB is built within the unit. So if you want to, you can add 32GB in the slot by buying an outboard microSD card (or 16GB, 8GB, 4GB or 2GB).
The unit lasts a long time if treated properly–I’ve had one for 2+ years, and it still works although the little nub on the power button has broken so you have to use a penpoint to slide it on. (I got a replacement). Despite charging and recharging every few days, I have had no problem with battery life.
But if you drop it a lot and use it like a hockey puck, it won’t last as long. And if you are brutal in the way you plug and unplug your headphones, the headphone jack is a weak point that can fail.
But you should have your music backed up elsewhere than the Fuze. There’s no such thing as a “shell,” but you could load a new player from your backup. Or you could put your music on a microSD card and move that to a new player. (But you should still keep a backup–cards fail, too.)
As to organizing, it’s flexible if you want to tweak a little.
If you look under Music and scroll all the way to the bottom of the list, you’ll see Folders. You can search by Folder the way you would on your Windows desktop. So you could just organize by folder names if you already have those organized.
Or you could use the Fuze’s database categories.
Album, Artist, etc., are taken from ID3 tags, which are electronic labels that are part of each mp3 file. You can make the Fuze reorganize those by changing the tags to trick it. So for instance, if you have an album called Brandenburg Concertos but want to put all your Bach together under Albums, you could edit the ID3 tags on those albums to change the album title to Bach–Brandenburg Concertos (or J.S. Bach, whatever).
A great piece of software for doing this is mp3tag, which is free.
When you install it, allow it to add itself to context menus. Once it is installed, open it and go to Tools/Options/Preferences/Tags/Mpeg. Under Write, choose ID3v2.3 ISO-8859-1. Those are the tags that work best on a Fuze, so those should be your defaults.
Then go to one of your album folders, right-click and choose mp3tag to open it. You should see all the tracks. If you want to change the album title (for instance), just highlight them all and change the album title in the left-hand panel, and (under File) Save Tag. Or change anything else you wish for your own way of cataloging.
Unfortunately, there is no universally accepted formula for the official tags on albums–the ones that are found online if you convert CDs, or come with mp3s you buy online. Classical tags are especially messy because there can be soloist, orchestra, conductor, composer, etc. So the ID3 tags on your classical albums could probably use some editing anyway.
Try to streamline if you do edit your tags. There is a character limit on how large a tag the Fuze can read, and classical albums sometimes put a strain on it.