you just need to smooth out all the rough edges, and once you get everything lined up, just mark some points where you want to put the screws and your done.
no need for custom fenders.
if you end up taking it to a professional shop, i recommend taking it to a custom shop that have extensive experience in custom work, and not some "professional" body shop.
i've had a lot of experience with professional body/paint shops and they always never do a good job.
NSX requires a custom shop that understands "show cars" like the guys that do the alpine cars.
then there are your professional body shops for those ok jobs that youre never satisfied with. but then again they don't charge or make enough money to really care to do a perfect show quality job.
prepping is the hardest part of all. it takes a rediculous amount of time to get any piece perfect whether its OEM metal or ABS, a polyurethane wing west kit, or a fiberglass kit.
FURYNSX has some pics i believe, and DONWON did a pretty good job too.