Freehub replacement

[Gadget]

Thanks for the great how to vids.
I have a '98 Giant XTC mountain bike
Shimano Deore XT 9 speed cassette
I believe XTM770 freehub
Quick release axle w/ Sealed bearings
Mavic 6106 rims w/ X223 4 bolt discs
I can't get the freehub off?
Please tell me I'm missing something and I don't have to replace the whole axle assembly because the freehub is seized.
The allen bolt inside the hub is 12mm and it won't turn in either direction.
Is there a wrench I don't have to spin off the free hub somehow.
HELP!

[cyclerUK]

http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Deore-XT/SI_3CZ0A_002/SI_3CZ0A_002_EN_v1_m56577569830621150.PDF
This Shimano Instruction doc' says the allen key is 14mm?
But is the hub a 770?
Freehub exploded veiw:-
http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/FH/EV-FH-M770-2699A_v1_m56577569830646670.pdf

[Gadget]

Could be 14mm, since I don't have an allen key that fits I am using a star drive tool that is long enough for the shaft to reach in there. Whatever it is it fits. I am ID ing the hub based on what comes up for my Shimano drive train. If you know something I don't, please enlighten me.
Thanks for the links, they help some. I would say I have an 775 hub based on those details. Curious, that I have a sealed bearings as apposed to loose ball bearings in a race. Is this unusual? All the details on these links show ball bearings as do most of the tutorials on hub work.

[cyclerUK]

Sorry Gadget but I know nothing extra ontop of what's in the Shimano Doc's.
The retaining bolt will be normal thread.. ie- Anti-clockwise to undo.
But it will be very tight!
A possible alternative is to put the tool in a vice and turn the wheel to undo it.
But be very careful not to damage the wheel / spokes.
Consider buying / borrowing the correct allen key tool as well.
Maybe a trip to a good bike shop is in order.