you will find 2 buttons under the front of the 6400. They will be between the 2 front feet.
press them up and pull outward on the front cover. there are 3 pressure fit tabs up each side
of the front cover. I found using a flat head screw driver helped to pry them free as I was
pulling the cover out. Be carfull not to damage the cover. the top bezal removes the same way 
but does not have the 2 buttons and is in much tighter. next locate a screw in the back of the
system very close to the top. unscrew it and slide back the top cover about an inch then lift
up straight. Now you have access to the wiring thru a cutout on top of the system and the bay
area thru the front. Reinstall in reverse order. You will have to buy a SCSI mounting kit (the
one from ProLine is very good and has an extender cable for the SCSI and Power lines
http://www.proline.com/6400.html).

Tom