Technically the migration of single entities (pages, CFs, assets) should not be a problem, because you can use an ETL approach and transform the exported data into a content-package format (or something else) and then import it into AEM. That's probably not the biggest issue, and can be automated
I see rather a problem with the structure of the content. AEM requires you to create a tree structure for your content, and this structure should never be arbitrary, but rather it should be considered and designed carefully.
In my opinion this is the hardest part.