The Train to met Life Stadium only runs for special events, The Siyum is officially a private event. The same holds true for the buses as well, You will need to call NJ transit. Its possible the Coach Company Bus will run from the Port Authority.
Hopefully the Siyum organizers contacted NJ transit , notified them about the Siyum and asked if some public transit could run (At least the buses)
if All else fails, take the NJ Transit to Secaucus and take a taxi, its only about $10 to Met Life and I am sure you will easily be able to find others to share the ride with you