I don't know anything about the G-Force axle. In fact I've never heard of them. If its a replacement axle, you need all of your hubs, and some lock nuts.
If it doesn't specify its a replacement axle, then they should specify that you have to use their hubs.
To take off the axle you need to take off the wheel hubs. They are splined, so you should be able to tap them off once you take off the hub nuts. Then take off the sprocket hub. Same thing. Splined, so it should tap off. Then you need to slide the axle out of the carrier. The stock carrier can be tough to get the axle out of. Then take the brake hub off.
When putting the new axle back on, do everything listed in reverse order, and be sure to torque the axle nuts if you use 2. If you use a lock nut, just make sure its on there good.