My NISMO came with the mud flaps from the factory but they look like they are held in place with plastic snap fittings. I bet it you look at your truck the holes are already there, and you probably only have to line them up and insert the fasteners!
Also, IM jerseyparts, he works for a Nissan Dealership and sells the mud flaps on YOURNISSANPARTS.com, I bet he'd know how they mount to the truck!
FuzzyRag, It is a simple install.
05 Nismo4X4 is right, there are already pre-drilled holes which are currently covered by push pins, all you have to do is remove the pins; align the guards; screw the supplied hardware in and you are pau (finished).
it helps if you have a short handled phillips screwdrive. OEM splash guards perfect fit, maybe a five to ten minute install. Goodluck!
All you'll need is a stubby phillips screw driver or one that can bend 90 degrees since you need to get inbetween the rear wheel and the well (you can turn the front wheels all the way left or right to get more access to the well up front) and something to clean the area with. The rear guards come with all mounting hardware and mount to existing holes. Up front, the guards come with screws that replace shorter existing screws holding on some plastic trim. I think it took longer to clean the areas than to actually mount the guards (I like things shiny!) and took all of 10 minutes. Be careful and don't overtighten the screws. The guards and fasteners are plastic and will crack if screwed down to tight. It's money well spent and will protect the bottom part of your truck from all the nasty stuff on the road (anyone ever run over gum? Yech). Good luck, I'm sure you'll be able to handle it.