The Mothership Wardens Operations Manual walks you through prepping both a session and a campaign. It’s one of the best published examples of that that I’ve ever seen.
The AL players pack (free on DMsGuild) includes the Content Catalog which answers most of your questions (it has a list of AL mods and documentation for running the hardcover adventures under AL rules).
DDEX and DDAL are the same thing. The DDEX designation was a holdover from the previous...
The standard cover looks like it’s composed of four or five different photoshop layers that don’t quite work together. The hero seems to be throwing his spear at something in the tree, and the hydra seems to suffer from the same ailment that makes my senior dog wipe out if she takes a corner too...
There‘s an entire Adventurers League campaign set in the Moonshaes. 34 modules plus the convention-only specials. They’re slowly making they’re way onto the DMsGuild, 7 so far.