You could set up a temporary account on another webhost, telling them that your website is undergoing maintenance, and return back here when your account is moved over.
you can add it as parked or addon. Parked domains are just an alternate name for you main domain.
As for the nameservers, use ns1.x10hosting.com and ns2.x10hosting.com
These addons have been disabled temporarily, but they will come back. The rep button is still present though. You may want to read http://x10hosting.com/forums/tutorials/102072-x10-community-rating-credit-system-explained.html.