How do I proceed on Z working Visa after receiving Invitation letter

I received my invitation letter a week ago, but I thought the embassy was still working on Saturdays but found out otherwise in searching. They want me there on Monday, February 13th, however I thought I also needed apostilled documents and sent it via Apostille PROS after the U.S. State Department told me 'not notarized, no apostille'. A friend said to go to the U.S. Embassy - Seoul but I can't stop working before I have the Visa (maybe I can still find work in Korea?). Anyway, can a travel agent give a 'Z Visa'? thanks for any and all help - it's probably my last chance as I missed 2 already (my age is over the hill)