Take a quick look at this. Maybe more later:
http://www.eastern-orthodoxy.com/mysticalprayers.doc
The usage in St. Cyril of Jerusalem (AD 387) is not exactly 1c. There is no doubt that the switch to "ιερεύς" meaning Christian priest occurred at some time, and that paragraph shows that it occurred as early as late 4c.
The question is, do "episcopos" and "presbyteros" in the New Testament refer to consecrated Christian clergy or not. I think it is plain that they do, in light of Acts 6:6 (consecration of deacons), 1 Timothy 4:14 (Timothy ordained into priesthood, although later we understand that he also functioned a sbishop, ordaining others), 1 Timothy 5:22 (Timothy to select carefully whom to ordain) Titus 1:5 (specific instruction to "ordain priests in any city", followed by instruction on how they are to be selected). 1 Timothy 3:1-2 speaks of the "office of a bishop"; Acts 20:28 refers to bishops "ruling the Church". "Episcopos" and "presbyteros" are indeed used, it seems interchangeably (cf 1 Timothy 4:14 and 1 Timothy 5:22), but the hirerarchical nature of the Early Church is evident from these verses.