Once you upgrade to Crusade, you will get a new "my games/GC3Crusade" folder for your custom content. If you have subscribed to Steamworks content, Steam will automatically redownload the content into this new folder. However, if you have created custom content that is not in Steamworks, you will need to manually copy it over:
Copy these folders:
Into My Games\GC3Crusade and you'll be all set.
A couple of notes:
- Steamworks subscripted items should update when you run Crusade.
- If you've subbed to a lot of content, it may take awhile for Steam to download it when you start up the game.
- Your mileage with mods may vary. I would suggest not copying over the mods until the author has had a chance to update them.
- Save games from the original game are not compatible with Crusade.
Please let us know if you have any questions!