The only problem is that Treaty of Champions (A H&M Expansion) has Crow Hags which were never in the 1st Edition. Other then that the H&M Collections have all the 1st Edition Monsters. I believe the H&M Collections also fixed some of the CK Cards.
Thats not entirely correct. There is also Shards of Everdark, which contains the "Dark Minotaurs" which are also new (like the crow hags).
A good place to start looking for information about the changes between the CK and the H&M sets is over here: