Yea, probably best to treat it as downloading a new game
There's the manual, which was reworked a while ago and is probably as up to date for 5.010 as 2.001L's manual was up to date for that version (which is to say, it should still get the general things right).
The tutorial is up to date, though, shouldn't be any problems there. It doesn't cover everything, of course.
And then there's the wiki, which is typically great for finding detailed answers. Even it has, ah, "aged" bits. But it's an ongoing work by the staff and some community members.
And if anything isn't answered on any of those places or the answers don't seem up-to-date, your best bet is to just ask here