Is there a guide on how to install the header. Shops out here try and screw marines over a charge 400 just to install it
First, a bit of a clarification. 9th gen civics don't have an exhaust header. They have a collector/downpipe.
Second, the following DIY is good for installing any downpipe and exhaust:
http://9thcivic.com/forum/threads/full-race-3-downpipe-and-catback-exhaust-system.8505/