I assumed 556 would be 500 block, I see on a map GCS is a short walk ... thanx
The most comfy and consistently ontime way to do this is the Coach Bus out of EWR, get on at terminal arrivals doors, get off at the Bryant Park (42nd Street & 5th Avenue) stop. Walk about 3 blocks to your destination. Walk back after and jump back on a return bus to EWR.
http://www.coachusa.com/olympia/ss.newarkairport.asp
Map from Bryant Park to Consulate,
http://g.co/maps/vb9va
$27/roundtrip/person though maybe cheaper if you look around.