I'm not sure making two posts is a good way to get the info you need... especially when the only difference is an extra question mark. 
Anywho.
Endless universe is as far as I know Dark Avatar and Twilight of the Arnor together, but not needing or including Dread Lords.
I saw a copy in GAME the other day for about £25. So it is out in retail here in the UK. I'm in far west Wales, so unless you're somewhere more rural than me, you should have no problem finding a store that has the game in stock. 