Hi, I've had to do this myself a few times.
What I do first is to remove the plastic around the steering wheel, think there are 3 torx (star) screws size 15 or 20. 2 at the bottom near the front, and 1 on the bottom near the back.
Look underneath you should see them.
Then at the back of the steering wheel, there are two clips that need to be released, I use 2 fairly substantial flat head screwdrivers, and prise 1 so far, and then prise the other until both clips are released, the airbag unit should then pop up.
Be careful when removing it as it is connected by 2 or 3 connectors, once these are released, the module can be removed. But be careful not to drop the module, it might go off.
The steering wheel is straight forward, think its a 50 or 55 star bit. Just remember to line the wheel to the mark when Refitting or wheel won't be straight when going straight.
There are 4/5 connections to remove from the comm unit, you need to undo a retaining collar for the unit to come off.
When refitting, the connectors are colour coded, grey brown blue, just remember to put them in the right connections.
Also when comm unit is fitted, but before steering wheel etc, remember to push a black collar through the comm unit until it clicks, or when the steering wheel is refitted, and you turn the wheel, you will snap the wires to the horn/airbag and the unit will be knackered.
I know this because I've done it after replacing my comm unit, I now need a 3rd unit which is £300+ new. And I have a unusual part number.
Hope this can be of help to you, it doesn't take too long, just be very careful with connectors etc.
What was wrong with your original unit?? My original one kept switching headlights on and off when ever it liked. And I don't have auto lights etc.
Any more help let me know