If I follow your meaning, you will need a script that:
1. Check to see if ED-E is alive (don't need any more bodies raining from the skies, they fixed that before we got the game!)

2. Checks to see if Ed-E is next to you, and if not, move him to you (if you want that).
3. Check to see if ED-E is is already following you, and if not, make him follow you.
4. If/Or this is just a quest, check to see if the quest is already running, and if not, start it.
An ounce more of requirements please?