Did the Greeks need Jesus to die and rise again in order to be saved?
Yes. According to the context, unless Jesus died, spent three days and three nights in the grave, and was resurrected from the dead, there was no salvation for those Greeks. This points forward to the gospel going to the Gentiles, showing that salvation for Gentiles depends on His death and resurrection.
Les teaches that those Greeks needed the same redemptive work: Jesus had to die, spend three days and three nights in the grave, and be resurrected, otherwise there was no salvation for them. He explains this shows Jesus already looking forward to the time when the gospel would go to the Gentiles. Les notes that from Genesis chapter 12 until almost the Apostle Paul, practically no Gentiles had access to salvation, though there were exceptions such as Nineveh, Ruth the Moabitess, and Rahab. Paul makes this plain in Ephesians chapter 2, writing to Gentile believers at Ephesus about their former state as Gentiles in the flesh, called uncircumcision by the circumcision made by hand.