LinguaPlone is the multilingual/translation solution for Plone, and achieves this by being as transparent as possible and by minimizing the impact for existing applications and Plone itself.
It utilizes the Archetypes reference engine to do the translation, and all content is left intact both on install and uninstall - thus, it will not disrupt your content structure in any way.
LinguaPlone doesn't require a particular hierarchy of content, and will in theory work with any layout of your content space, though the default layout advertised in the install instructions will make the site easier to use.
These details are provided for information only. No information here is legal advice and should not be used as such.