I know that daemons changed a lot in the 8th ed change over but I can't find it anywhere! I've read on these forums that blood crushers are monstrous infantry, that greater daemons have thunder stomp. These are key rules that make a huge difference in the game. Can someone point me in the right direction as where I may find these changes? Thanks in advance guys!

What you need to find is the official rulebook Errata/FAQ and the one dealing specifically with Daemons. Both are available on the GW website.
Direct Link to all the PDF-files
Now, for some reason GW has made it a bit tricky to find these.. This is what you need to do:
Go to the Main Page of the GW site.
Click on the "Gaming" category.
The last alternative in the dropdown menu is called Errata/FAQ articles, click here.
On the next page click on "Warhammer Frequently asked questions".
On the next page click on the green "Next" button.
Now you're home.

It's true that they forgot to enter alot of Daemonic Units into the main rulebook for some reason. Probably the biggest single blunder with the 8th Ed book actually.. So they are mentioned specifically in the Main Rulebook Errata.

The other thing to note is that changes like Stomp, Thunderstomp,and Vangaurd are not special rules that units got individually in the update, but that they got as a result of their unit types. So GD's Thunderstomp because they're Monsters, and Seekers Vanguard because they're Fast Cav. Means figuring out the changes take a little more thought.

Oh, and the other way to get to the FAQ articles is just to go anywhere on the GW site and use the search bar for "FAQ".

Thanks guys! I'm new to these forums but so far you guys have been very helpful.