but still know hardly anything about it
Join the club, Linux is a Lady, there's mistery, suspense and mistique...you'll never get a grip...trust me, I'd know...
then a new version comes out, and it's back to square one
...umm, that's subject for debate....in my very humble opinion, but if you know the base, you're set. Fedora 8 was my starter, what I learned (command line wise that is) was pretty much applicable to the ones I used next (Arch, Xubuntu, Bodhi, Debian and now Manjaro)...
Unless you really deviate (like I had with Solaris) and discover AFTERWARDS that "this is not Linux anymore"...hehe,
And again: welcome back...