It might be the biggest reveal, but... Sam doesn't know that it is, nor did he hear it properly nor did Gilly pronounce any names properly. Hence, I think, it went over his head. :-P So not totally OOC, I don't think.

About the warging, in the awesome swedish podcast I listen to after watching every episode this has been discussed A LOT! And I mean, he's been able to warg into most things so far. Even Hodor! Who might have been slow-witted, but was still human. I am guessing he would be able to, but I also think it would cost him. So... Maybe he'll do it?