I do not believe that you have much reason for concern... just put the old content on the new domain and upload it.
The content is no longer at the old location so there is no longer a duplicate.
Also, there isn't really a duplicate content penalty. The result of duplicate content is that some copies are filtered - the copies with less authority.
* "It's not the size of the dog in the fight that matters, it's the size of the fight in the dog." Mark Twain
* "Free advice isn't worth much. Cheap advice is worth even less." EGOL