Hi everyone, I have another questions, this time about Mammoth riders. After I play them I cannot play any other card. As far as I understand that means that I can still use Ambush and I can still put card in and out of shadow.....is that about right?

Yes. "Play from your hand" and "Put into Play" are different things. "Play from your hand" occurs when you marshal cards in the Marshalling phase or when you play Event cards. "Put into Play" occurs when you use card effects, including Ambush, to bring characters, locations and attachments into play.

Oh, another thing: Bringing cards into shadows is "Playing a card" when you pay two gold to do it during Marshalling. It's not "Playing a card" if you use some card effect to return a card from play into shadows, like Syrio or KL Arya.