Ceramic coating won't protect it perfectly, but then neither will PPF: It'll still chip, it'll still mark, it'll still be as noticeable. It may not chip as easily as regular paint, but between PPF and ceramic coating I don't think there'll be a lot in it (I've accidentally got coatings over my clothes when applying them, and the patch dries to go rock hard!). It's also how different the panels will look in daylight, with PPF on some but not others.
Each to their own fella, but honestly I don't think you'll be as happy with the results after 6 months as I think you want to be. I'd rather you saved your money instead. Def budget to get the detailing done before the PPF, as I can promise you now that the car will be swirly swirly upon collection, better to have it arranged beforehand than to be surprised on the day. Don't forget you can get the guy to do all this at the Nissan dealer before collection, so even if you delay collection for a couple of days it'll be fine.