From what I have read on the Samsung and other forums, you need to apply that firmware patch to any 840 or you will get the super slow down on Reads quite quickly.
Mine has that Rev firmware now also.
Doesn't the boot disk give a selection of disks to upgrade ?
If not, can you drop it in as the system disk and boot off the CD and flash it. You don't need data, even though it spends 20 minutes mucking around writing stuff on an empty disk. No idea what its doing all that time.