I've been assigned the task of migrating my site from SharePoint 2013 to Office 365. I've decided to use Microsoft Fasttrack for migration but have no idea where to start from since there is no technical document avaialble.

My question is:

Are there any changes that needs to be done before Migration? My current site has a lot of custom webparts, Event Receivers, Workflows (Designer and Custom) that have been developed in Server Side coding. Is there any technical documentation available stating step by step procedures involved in Migrating to Office 365 from SharePoint 2013?

Any help is much appreciated. Thanks, Sheldon