I find these directions to be a bit easier for the method you are trying to use.
http://forum.xda-developers.com/showthread.php?t=584029
Once you hold down Volume down/Power...Are you pushing the Home button to get into the Recovery screen? Are you flashing 2.0C? Are you making sure to wipe before you attempt to flash the ROM? You have to Wipe before you flash the ROM. Quite frankly I don't rename my ROM zips, I leave them named whatever they are named when I DL them. Go over the directions I gave you and see if that is a bit easier. It sounds like you have gained root if you followed your original directions. Make sure you back things up as well, I would make a Nandroid backup before attempting to flash.