It is position dependent.Never raise anything from UTG SB or BB pre-flop.
This is completely wrong, you can raise hands from any position, you just need to know what you are doing
AA is not as strong as in NLHE.
With 5678 be careful even if you hit someone holding xx9-10 has you beat.
I just blew off a buy-in with 3 aces on a paired board to an opponent holding A-2 on an AAx2x board. It's a tricky game,I should have folded when the board paired and he raised me.
Google omaha and learn the game first,
http://www.pokerstrategy.com/ has good stuff on omaha in it's silver section.