Relax, take it one hour/day at a time. Try to build a list of people you can contact for support if needed, I imagine you and your boss aren't the entire IT team. If something happens and you get stuck call someone, its ok (especially as an intern) to say 'I don't know I need some help' especially if something is on fire. Try to find or define a plan of what's going to happen, eg at X time someone will start the roll out then x & y should happen and finally z means success.

Above all else: If your boss knowingly left a junior employee to do something with 0 training or guidance, any fuckups are on the boss. Don't beat yourself up about it, life will happen and you will get through it.