GnomeDruid was implemented as a container for GnomeDruidPage abstract objects, which are implemented by the GnomeDruidPageEdge and GnomeDruidPageStandard widgets. Instead, GtkAssistant allows any widget to be a page, and implements per-page settings (such as page type or title) as child properties. So instead of:

/* Page 1 */
page = gnome_druid_page_edge_new (GNOME_EDGE_START);
gnome_druid_page_edge_set_test (GNOME_DRUID_PAGE_EDGE (page),
                                "Welcome to the assistant, it will make your life easier");
gtk_widget_show (page);
gnome_druid_append_page (GNOME_DRUID (druid), GNOME_DRUID_PAGE (page));

/* Page 2 */
page = gnome_druid_page_standard_new ();
gtk_container_add (GTK_CONTAINER (GNOME_DRUID_PAGE_STANDARD (page)->vbox,
                   create_page1 ());
gtk_widget_show_all (page);
gnome_druid_append_page (GNOME_DRUID (druid), GNOME_DRUID_PAGE (page));

/* Page 3 */
page = gnome_druid_page_edge_new (GNOME_EDGE_FINISH);
gnome_druid_page_edge_set_test (GNOME_DRUID_PAGE_EDGE (page),
                                "Now you are done, your life is easier");
gtk_widget_show (page);
gnome_druid_append_page (GNOME_DRUID (druid), GNOME_DRUID_PAGE (page));
    

You have to write:

gtk_assistant_append_page (GTK_ASSISTANT (assistant),
                           gtk_label_new ("Welcome to the assistant, it will make your life easier"));
gtk_assistant_append_page (GTK_ASSISTANT (assistant),
                           create_page1 ());
gtk_assistant_append_page (GTK_ASSISTANT (assistant),
                           gtk_label_new ("Now you are done, your life is easier");