Hi there. I'm new to polyamory too, it's quite a whirlwind isn't it!?
I just wanted to say that as far as I understand it polyamory should be something that both partners are happy with. I think it's fantastic that you are giving it a go and trying to adapt but don't fall into the trap of saying yes to something you're not happy with just because you're afraid of losing your husband to this woman. Lay your own boundaries.
Having said that, I think if you could come to terms with it you might find it (as I do) really healthy and fulfilling. Good luck.