pop the hood jack up the car look at stock exhaust manifold from the open hood point of view. Now crawl under the car and look at the exhaust manifold from under the car and notice where it bolts to the cat. If you cant figure out how to put it on after looking at in from the points of view that I just mentioned then it would be wise that you not work on your car. They are very simply to do just look at it and it will all come together. As far as the o2 sensor goes (the only forseen problem you should run into) unplug the o2 sensor at the harness and take the stock manifold off with hte 02 sensor still in it. With the manifold off the car take the o2 sensor off and put it in the new header.

 

yeah like i said its easier to wait till the manifold is out of the car to get the o2 sensor off because its very hard to get out you may wanna just spray it with liquid wrench wd-40 or some other form of penetrating oil and let it sit for awhile then find the largest longest wrench you can find that will fit on there cause chances are yuore gonna need all the leverage you can get. And its threaded normally so if youre struggling with it and it isnt coming out DO NOT think that it is reverse threaded because it IS NOT!
Robster

 

I think that was in reference to the definition of header or headers.