To change the user name go to My Account, select Request Username and fill out the form.
In case the name is not changed in a day or so, do a dropbox http://www.edge-gamers.com/forums/forumdisplay.php?f=852 requesting your name change. Select Name Change in the prefix.
As for the e tag check maul( eGO Tools -> Maul Home ) and see if the tag is there in Groups(it will show up a little later if you're a new member). If it's there just add the =(e)= tag in your name and contact someone from the PSC Div in TS or when someone more knowledgeable in this matter will answer in this post.
the tag shows up as long as you do not change your name once you join the server and your forum account is not considered inactive. If you do not go onto the forums once every week or so, it will be marked inactive.