Tips for an AoM Player wanting to learn AoE2 DE

Hello guys, i'm an average ex AoM player (not good, not horrible) wanting to learn this marvelous game, and i have some questions for you:
1 - What are the basics i should learn first? (Building order, eco micro, militar micro...) some kind of roadmap would be nice...
2 - What are the best civs for beginners?
3 - Should i join the multiplayer already?
4 - What are the greatest differences between the games?
5 - What site is the best for my learning?
6 - Any more tips?

Sorry for the poor english...