You can also use a simpler approach and define implicit styles for TextBlock, TextBox, DatePicker, ComboBox, and Button controls in the App.XAML of your Silverlight application. Even though the EditorWidget control does not have a Style property for its internal FeatureDataForm control the implicit styles will automatically apply to the contents of your data form and you won't need to go through the process of replacing existing buttons, handling events, styling your own FDF, etc...
Hope this helps.