Thank you all so much for your help! The advice on this site has been invaluable and I don't know how I would have done this otherwise!
Just an update, in case someone is reading this thread and wondering what the outcome is (I don't like it when I read something like this and don't hear the ending!)...it took us about 2 months to complete our coop and in the mean time our hen was free ranging most of the day and then put in her make-shift coop at night. A friend donated 6 3-month old pullets to us! While we were at the "baby thing" I decided to get 2 more Black Copper Marans as there's a local breeder here that offered them the same age! Ironically enough, DH and I decided NO roosters and as soon as we showed up, my husband spotted one he wanted! LOL! So we ended up with an Ameraucana roo...super sweet disposition!
Well, doing the sneak-her-in-the-henhouse-at-night-trick did NOT work for us! The smallest (a turkey) about got killed and our hen was angry, just paced the pen all day (I suppose wanting out to free range), so we let her out...a couple weeks later checked a "baby"...LICE!!!! Apparently the rooster had lice!!!
So later that same day our original BR got sick...apparently with Foul Pox and Cocci

Sad, the day we got the med for her, we went out and she was gone...apparently a hawk must have picked her up! What are the chances?!?!
Moral of the story is, next time, I think I'd go the chick route...I've learned more than I ever wanted to know these last couple months about chicken disease! Also I would get them vaccinated if that's an option for Cocci, if they're going to free range...I was and am still aiming for organic eggs, however, with our summer here being so rainy and a perfect environment for parasites, I think that it's worth it! 3 months seemed to be an okay age to introduce them (they were really good at getting away from the fat lady, for the most part) but I think I'd leave them in sight, but apart for several weeks first.
Hope this helps someone else out in my same perdicament!