Some models don't have the clutch mechanism, but are driven directly from the motor (and the belt cover which is shown as the clutch cover is now part of the soleplate); in that case, it may be simpler to just remove the belt from the motor spindle.
If you've had the vacuum cleaner more than 2 or 3 years, consider changing the belt at the same time, they are not expensive
Some DC14 units don't have the clutch mechanism (the motor drives the rotating brush directly with the rubber belt), and the "cover" is now part of the soleplate (removed in step 2), so just skip this bit....
On some models, the motor cover is white
Great guide! A useful tip for getting the motor (or specifically the rubber cover) into the motor case: smear some washing up liquid or liquid soap around the inside of the motor case, and the rubber will slip in a lot easier. Keep an eye nf the rotational position of the motor (so that it fits the hole at the axle end correctly), and make sure you don't trap the 2 power wires.
Don't confuse the top left screw with the (non-recessed) screw that holds on the small piece of pipe.... the one you are looking for is recessed like the top right one.