I guess another way of looking at it is, what's involved going from non-nismo to NISMO because more than likely the Stillen front end is meant to fit the non-nismo, right?
The only difference between the NISMO front end and the non-nismo are the Autech/Yamaha dampeners, the under tray and the fender liners.
Other than that...the bumpers clip on and bolt on exactly the same. I'd check out Stillen's website and read through
their install manual.
Looks like there is some drilling, windshield washer reservoir needs to be moved, some gluing is involved. I dunno, read through it and let us know.