The first thing you should do is disconnect the battery and wait at least 5-minutes - This is to be sure that the airbag won't deploy while you're working on it. I'd highly recommend putting a piece of masking tape (with a line drawn on it) on the steering wheel, and a piece on the dashboard while you sit and wait. This way, you'll know the exact position the steering wheel is meant to be in when you reinstall it. Make sure that your wheels are perfectly straight when you do this.
The next step is to loosen the two Torx head screws behind the steering wheel on each side (they won't come right out, they just become loose). This will allow you to pop the horn pad off and disconnect the airbag connections (just be careful not to pull on the actual wires for the airbag). Put the horn pad in a safe place, but make sure that the face of it is pointing
upwards.
Once that's done, you can now loosen the centre nut on the spline. Make sure you only
loosen this at first, as opposed to removing it entirely, as this will stop the steering wheel whacking you in the face when you're pulling on it (believe me, it hurts). With the nut loose, place each hand on either side of the steering wheel and begin to rock it until the wheel becomes loose. One you've done that then you can remove the nut completely and slide the steering wheel off the spline.
It's a relatively straight forward procedure, and hopefully shouldn't take you very long at all. Just make sure that the battery is disconnected first

. Best of luck.