Is the car petrol or diesel? The petrols are generally easier to activate cruise control in. For the diesel you need the UCDS program and lead from Russia. Otherwise Terry Evans is your Man, he's converted loads of these car to cruise control over the years - I'm lead to believe he's uses a few of the facebook groups so can probably be contacted through thosse.
As for the steering wheel, I believe they're all wired up the same, but don't take my word for it! Some of the cruise buttons are layed out slightly differently model to model, so might be worth taking off your wheel to check the part number matches the new one.
To remove, disconnect battery (very important when messing with the airbag!!!). Remove the steering column shroud and lower the steering column to enable you to gain access to the back of the wheel To get the airbag out there are two clips that sit inside the areas i've marked (they are clips which are fitted to the airbag and hook over the feet at the bottom that you can see sticking out). To Release the clips slide a very small screwdriver or pick down the little curved channel and release the clip as you lightly lift the airbag away from the steering wheel. Sometimes after releasing one clip it will click back in as you try to release the other side!!!!
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The problem here being is that it's easier with the wheel turned 90 degrees..... but then when one is done, you have to turn the wheel the other way!! I didn't tell you to do this but what I did was turn the wheel one way...switch off and release the clip, then switch on...turn the other way and release the clip, then switch off and disconnect the battery and leave to stand for 20 minutes or so before disconnecting the airbag just in case there is any residual power left in it. But I didn't tell you to do it that way lol and I claim no responsibility if the airbag goes off!!
Once the bag is lifted away from the steering wheel, take a photo on your phone of where the wires go to help you to put it back together. Disconnect the wires (slide the orange clip outwards on the yellow connector before trying to remove the yellow part). You then need a ratchet, extension bar and 24mm socket, undo and remove the bolt then the wheel should lift straight off as you wiggle some of the wires out of the hole in the back. Just be careful that the clockspring stays in place as the wheel comes off.
Refitting is the reverse, but threadlock the wheel back on and torque it up.
Cruise can be enabled with forscan on the petrol I believe, but like I say, you need UCDS for the diesel.
Hope this helps!