I will be staying at a hotel in the port area of Marsaille, France. What is the easiest way to get to the airport and about how long willl it take?
You can take either a direct train from the Marseille-Saint Charles station or a direct bus that leaves from outside the train station. See this page on the official airport site.
I assume you mean the "old port" area in the center, not where cruise ships dock (which is not near the Vieux Port area at all). To get from the old port to the St. Charles station, you will need to take the Metro or a taxi (it's uphill). Of course, a taxi all the way from the Vieux Port to the airport is the "easiest" way, and it doesn't take too long.