do u have the new casing with u now? for me, i like to remove the PSU first becoz u can move along all the wire together. dismantle all cables - IDE, SATA, Firewire. As for front panel, detach all cable - usb, audio, mic hdd led, hdd switch, reset switch.
then when all clear, it is easier to unscrew all mobo screw.
IIINM, the led mobo can works either way. doesnt matter -ve or +ve. correct me if i am wrong.
anyway, what casing ure changing to? Li-an Li perhaps?