Files to create

download tem from Files-Section

resume:

- add /admin/womd_customsearch_settings.php - backend settings for the feature
- add /templates/YOURTEMPLATEFOLDER/module/googlecustomsearch.html - the template for showing cse to customer
- add /admin/includes/classes/xtc_admin.php - refactored way of getting access data
- replace /includes/modules/error_handler.php - found this to be the place to "catch the no products found error" and not intereference with other modules / things like login / passwordlost / extened search etc.
in most cases you could just replace it.