i am new to this so take it easy me......i was wondering if it was to much of a pain to get a full header for my 01 zx3. how many exaust mods will i have to do??? just wondering if it's just worth it over a shorty header with an aftermarket cat
A Race Header should bolt right up to the flexpipe, but i should warn you, the header is a pain to install from the start.....especially if you don't own a lift.  It may not be worth it if you don't know anyone who can slide by the header in an inspection, and it could get costly if the (Kl)ops figure out you don't have a Cat....or any enviromentalist for that matter. It's not a pain to get one, unless you consider dropping over $300.00 on a header.....but it does make you open the hood more @ your local gas station. 
ive heard its a real pain in the ass to change headers. i havent changed mine yet but will in the very near future. if ur wanting a race header then u'll need the header, flexpipe, and exhaust of ur choice. if ur goin' shorty, then ud need the header, flex, high flow cat, and exhaust.
edit: and if ur gettin a race header, then ud also need o2 cheaters as the race eliminates the cat and it will throw a check engine light.