If your car is a Diesel, it is a straight forward job of installing the correct clock spring and steering wheel buttons. The diesel throttle body is electronically controlled.
If you car is a Petrol, you have to also install the cruise control module under the bonnet/hood and connect it to the throttle body. The Petrol throttle body is controlled by an accelerator cable.
I have driven both petrol and Diesel FD's with cruise control. The Diesel cruise control is excellent due to it electronic control. Very quick to change for changes in hills etc. The Petrol cruise control is OK on the flat straight roads, but is a waste of time when you hit the hills. It's ability to quickly control for hill changes is just too slow.