Events need a start date and trigger. Use civilization exists if you just want it to happen everytime.
You can create multiple decisions.When the event fires the recipient get to choose one of them and every outcome under it happens.To create uprising use annex or occupy,declare war and add army. If you want the population to convert to the new civ there is no elegant way.
The best is to remove population of the original vivah and add an equal population of the new civ.
Trigger: Civilization exists
Date:As per your choice but don't forget to add a start date
Outcome:Annexation. New owner: civil name
Declare war: Egypt,civi
Add army:as per your wish
Change ideology: rebels
Trigger another event:event name