All saved data (including game saves, Marketplace downloads, profiles and avatar props) are on the Hard Drives. Switching Xboxes wont affect those. BUT, you will need to do a license transfer of all your Live content to be able to play online properly.
Did this solve your problem?
Sorry this didn't help.
Great! Thanks for marking this as the answer.
How satisfied are you with this reply?
Thanks for your feedback, it helps us improve the site.