Oki, i figured the first part. I can do a {attribute_view_gui attribute=$:item.data_map.menu_title} or a {$:item.data_map.menu_title.data_text}
but i still have problems with the not() function how should it be used? the sdk explains this bad I think (http://ez.no/sdk/eztemplate/view/operator_list/)...
You might want to try {$:item|attribute(show)} or {$:item.data_map|attribute(show)}.
Also I would check the rights of the anonymous user. If you've created a new class, the anonymous user won't have the right to read it.. (I've burnt myself on this several times)
Try to give your section a name=test, so you can access the $test:item.... from the nested section.
I think your {section show} can be written like this:
{section show=ne($test:item.node_id, 131)}
{/section}
or you could use a switch/case statement: http://ez.no/developer/ez_publish_3/documentation/development/libraries/ez_template/functions/switch