Oh boy. Your guess is as good as mine...I'm going to bring a new kitty in, and I'm not looking forward to all of the uncertainty and time this will involve.
There are several threads about how to introduce a new kitty - a forum search for slow introduction should bring up some helpful ones. As tempting as it is, just letting her out and seeing where the chips fall is probably not a great idea, in my opinion. If things don't work out, it might be hard to backtrack and undo any negative experiences.
But maybe others will have some success stories for you. At any rate, I'll keep my fingers crossed that all goes well!