if you don't/aren't planning on driving, you should get off Logan airport.
Once there, look for the subway station. The "blue line" has a station "Airport" right at Logan. From there, you have to take the "inbound" or "westbound" direction to "Government Center" where you can switch to the 'inbound' directions to the green line. once there, you have to take it to "Park Street" and switch to the red line. There, "South Station" which is on the red line is only a couple stops away. It'll be much easier to walk, but since you are not familiar with Boston, you can just take the T.
if you go to
www.mbta.com you can have a detailed map of the subway in Boston.
Once at South Station, it's like very big station with trains, buses, commuter rails, subway. You can ask people at the desks where you can grab the train to Worcester. I believe it's either Peter Pan Bus or Greyhound Bus. They are not cheap, but they'll get you there. I am not sure about the Commuter Rail, but if it runs to Worcester, then it'll definitely be cheaper than bus.
you can check
www.peterpanbus.com or
www.greyhoundbus.com for detailed info about their routes.
Good Luck!! i myself have an interview on the 17th. Let me know how yours went!