How do I do it?
Is this something that takes an act of God to accomplish? Can the posts from an older version be moved to a new forum of a later version?
Also, Can a PHPBB forum be moved into a PHPNuke forum?
I'm a noob at this, so any specific details of this process would be much appreciated...
Moving the content of one PHPBB forum to another.
You can use mysqldump (or phpMyAdmin's frontend to mysqldump if you don't have a shell account) to dump the contents of the database to a text file, then import that text file into the other database (add a "USE database_name;" line to the beginning of the text file, then run "mysql --user=username --password < text_file_name" -- or, use phpMyAdmin. 
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