Information about instead of triggers is stored as it is for for triggers.
The definition query tree for a trigger is stored in sysprocedures.
Each trigger has an identification number (object ID), stored in a new row in sysobjects. The object ID of the view to which the trigger applies is stored in the deltrig, instrig, and updtrig columns of the sysobjects row for the trigger. The object ID of the trigger is stored in the deltrig, instrig, or putrid columns in the sysobjects row of the view to which the trigger applies.
Use sp_helptext to display the text of a trigger stored in syscomments. If the system security officer has reset the column parameter allow select on syscomments.text with sp_configure, you must be the creator of the trigger or a system administrator to view the text of the trigger through sp_helptext.
Use sp_help to obtain a report on a trigger. sp_help reports instead of trigger as the object_type of an instead of trigger.
Use sp_depends to report on the views referenced by an instead of trigger. sp_depends view_name reports the trigger name and its type as instead of trigger.