Having just changed my headlamps to an HID kit on my Spider 2.4 JTDM, I found the job easy but fiddly, especially if you have sausage fingers and it is -3 outside. For anyone attempting the task soon I offer one piece of advice:
The headlamp bulb retainer clip must be removed to put it around the wires to the bulb. Putting the clip back can be a nightmare, and you will drop the clip. After you have removed the clip to take out the original bulb, tie a longish piece of string to the front of the clip, and you won't loose the clip when you re-install it. You can remove the string after the job is complete.