The nice thing about Office 365 is that it lives in the cloud and is very flexible. You can migrate small trial runs of data to a trial Office 365 subscription and figure out what might go wrong when you migrate the entire organization. In fact, you should sign up for an Office 365 trial right now.
The trial is absolutely free, and you can be up and exploring the product in a matter of minutes.
Even if everything went as planned, the process took at least a half day and possibly a lot longer. With Office 365, you, as a business user, can go straight to the Office 365 website, sign up for a trial, and explore SharePoint in a matter of minutes!