Well, our exterminator came again on Friday...and proceeded to find one mouse in a sticky trap in the basement. So, he and my husband walked through the unfinished portion again and found a few more airways to plug to be on the safe side (which was done a few short hours later). From what he said though, he thinks that this most recent one was just that...one. He didn't see signs of any more.
And we just finished sterlizing the attic...all the mouse urine and feces have been removed along with bags and bags of yucky insulation. So now it will be really easy to tell if there is any new activity up there or not.
Here's hoping that they have learned that they are not welcome at our house.