How do I migrate an existing Drupal site to Drupal Commons?

Question

I have a Drupal site in production. The site's large enough that I don't think it's feasible to manually recreate the content types, users, etc. However, the client has decided that they want the site to be based on Drupal Commons rather than vanilla Drupal. How do I go about migrating my entire existing site to Drupal Commons?

My first thought was to install a Drupal Commons instance and use the Backup and Migrate module to move everything over, but wouldn't that remove all of the nifty preconfigured pages, views, and stuff from the Commons instance?