To start with, you should probably begin with my Upgrading a MOSS 2007 WCM Site to 2010 post.
Once the 2007 content database and site has been restored and upgraded to 2010, go to the Site Settings (e.g. http://sharepoint2010/_layouts/settings.aspx )
The Settings pages should have the original “2007” look to them. To upgrade the Settings site to the new 2010 branding, you will need to located the Visual Upgrade feature. ...