The best way to be ready to upgrade is to ensure you’re running the latest build of Nintex Workflow 2010, as available from here.
You can check to see which build you have by going to SharePoint Central Administration, navigating to the Applications page, and clicking on the licensing link under the Nintex Workflow section of that page.
Upgrading from older versions is possible, but build 2.3.5 or later is fully tested and supported.