Please ask GateIn questions in the GateIn user forums: https://community.jboss.org/en/gatein?view=discussions
This is an old forum for JBoss Portal which later became GateIn when it was merged with eXo Portal.
To answer your questions
1) yes, you can merge in new pages via the configuration files. Please look at the portal extensions documentation: https://docs.jboss.org/author/display/GTNPORTAL35/Portal+Extension
These links may also help: https://docs.jboss.org/author/display/GTNPORTAL35/Portal+Navigation+Configuration and https://docs.jboss.org/author/display/GTNPORTAL35/Data+Import+Strategy
2) yes, there is an option to export and import portal configurations. Please see https://docs.jboss.org/author/display/GTNPORTAL35/GateIn+Management and there is also an import/export gadget which will do this as well.