1) You can sign up with a soon-to-be domain, no problem. Just keep in mind you would have to access Cpanel and your site through IP/~username given to you in the welcome email.
2) This is also not difficult as it's just a simple change in WHM. I am sure all you would have to do is submit a ticket to the helpdesk and they would take care of this for you.
http://desk.surpasshosting.com