I just spoke to Nathan, our CTO, about the Schtuff transition. He told me that he’s working with Carl at Schtuff to finalize importing the Schtuff wikis to PBwiki. We expect to give the technical thumbs-up to the Schtuff team within 24 hours. After that, Schtuff will begin contacting its (our?) users to let them know how to migrate their wikis. As far as we understand, the trains are all running on time for the import to happen this week or early next week.
If you have questions, or to stay current on the latest Schtuff-transition news, check out this forum post.
PBworks Official Blog 
Is there a way to change a wiki so that it is private instead of public?
You can change your ‘Private/Public’ status through your ‘settings’ links.