Now, may be it will go smooth, may be it won't. Either way, it won't be your fault because you are an intern and the worst they can do is to fire you which is not so bad even though you may think that it is. Best, your boss probably has done this before and knows that its no biggie. If shit hits the fan, other people will get involved.
In case that you are the one "Responsible", use that as an opportunity to shine and show it to senior management. If things go bad, tell management "This is a great learning experience for me as an intern". When people find out that you are an inter, expectations will change.
One lesson learned for you: When your boss leaves something in your "capable" hands, ask these questions BEFORE they leave. Make sure you understand what's expected of you especially if things go wrong (they usually do with major updates).
You will do fine.