Fyi ~ most of the time the bumper clips will get broken or damaged when removing them for fitting these things or removing bumper etc. You can get plenty of Nissan clips on eBay. Much cheaper than Nissan dealers charge.
For example, link; http://www.ebay.co.uk/itm/Honda-Toyota-Nissan-Lexus-Bumper-Retainer-Trim-Clip-x20-/270719480465?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item3f08237291