The install is easy. Getting the rear deck lid off is simple on the coupe (the spider has an electrical connector in awkward place, but still pretty straightforward) - just 4 bolts under the hatch where the oil and water caps are. Remember to put masking tape along the sides of the deck lid before removing it as it typically ends up touching (masking tape is the approved McLaren method, as per the repair manual!).
You then have to remove the OEM rear bracket - 11 bolts if I remember right - and replace it with the new bracket that the wing struts will attach to.
The cutting is the most grueling part. My Agency Power wing came with a plastic template. I believe the Novitec comes with some kind of template too (they both fit the same way). The bit you're cutting is just plastic, so cut slowly, and it's pretty easy. Took me about 30 mins to do the left side my first time, then only 10 mins to do the other side.
Then just attach the struts, put the deck lid back on, and then mount the wing.
If you're experienced, you could probably do the whole thing in about 30 mins. A first time DIY, could take you a couple hours.