1) To speed up the upgrade, microsoft has provided some tools in order to upgrade your WSS 2.0 to version 3.0. Read the full article here.
2) Additionally:
"With the recent arrival of Windows SharePoint Services (WSS) 3.0, many administrators are faced with the task of upgrading their existing WSS 2.0 sites and data to their new WSS 3.0 environments. Though WSS 3.0 provides extensive tools that adequately migrate site data and upgrade site structure, additional work might be necessary to upgrade the structure of customized sites or site templates. However, additional work might be necessary to upgrade the structure of customized sites or site templates. Fortunately, the Microsoft® Solution Accelerator team has released the Upgrade Toolkit for Windows® SharePoint® Services Sites and Templates, which provides guidance and tools around this practice (see the "WSS Resources" sidebar). This column focuses on some of the challenges and solutions associated with upgrading customized sites to WSS 3.0 environments"
Read more about this Utility Spotlight HERE.
3) Below is an image of the WSS site and site template upgrade workflow:






