Combine name field and category :label on save
The first thing you want to do is add some debug code to see what variables you have to work with. Try:
If new_category is a number you'll have to load the label manually. Check out the function getListOptionsFromSchema(). You can pass it a fieldSchema to get the values for that field, eg: (untested code)
$fieldSchema = $GLOBALS['schema']['news_category'];
$valuesToLabels = getListOptionsFromSchema(fieldSchema);
$fieldLabel = @$valuesToLabels[ @$_REQUEST['news_category'] ];
But you'll want to use showme() on the different variables if it doesn't work at first try to see what data you're getting.
Hope that helps!