I don't know how the 6500 model compares to the 6000 model, but if it's similar I would strongly suggest you DO NOT pry off the back cover. Instead, open the front of the unit where the bag goes and slide the side bumpers forward. once the bumpers are removed carefully separate the upper and lower halves enough to see inside. Look for a clear plastic tube and disconnect it from the upper half. You can now open the unit.
the bish, September 2008