At your documentation you write "download and install the upgrade package on Your Orders" - so i´am wondering where to find these upgrade package.
I could download the Component, the Plugins and Modules...but i couldn´t finde these package - and if tried to update via the Component i get the message that the folder is in use.
there's actually no upgrader for 2.3.0 to 2.3.1. you can simply just install the newer version (uninstalling the old one first)
no data will be lost at all. All the albums, artists and songs will still be there.