Qumran didn't exist in 6 BC, that's the modern Arabic name. Joshua 15:61-62 lists the cities belonging to the tribe of Judah. The assumption is that its ancient biblical name was Secacah since Secacah is singled out as the Dead Sea settlement in the famous Copper Scroll from Cave 3.
I'm paraphrasing material from Carsten Peter Thiede's book "The Dead Sea Scrolls and the Jewish Origins of Christianity (page 14). Another good source, of course, is Josephus.
I mentioned Qumran in my first century novel and then went back and changed it after reading Thiede's book. I'm sure there's quite a lot about the Essenes out there. Although I'm not specifically interested in the Essens, here are couple of others that I've found helpful in my research:
Carsten Peter Theide, and Matthew D’ancona. Eyewitness to Jesus, New York, Doubleday, 1996
Carl J Somer. We Look for a Kingdom, San Francisco, Ignatius Press, 2007
Good Luck