ok, first, if you dont have one, i recomend going out and buying a Haynes or any other type of repair manual, they come in handy. You can get them at just about any auto store, if they dont have on for your car or year, they can order one(you can also find them online) but since your in a rush ill list the steps from my book, its for acura integra 1994-2000 so it should help.
Removal of exhaust manifold( header)
1. Discontect the battery cable from the negitve terminal. (youll have to reset your radio if you still got the factory one)
2. Raise front end of the car and support it securely on jacj stands( car ramps are better to use). Unbolt the brace and detach the exhaust pipe from the exhaust manifold. Apply penetrating oil (wd40) to the fastener threads if they are difficult to remove( they will be, so go get wd40).
3. Remove the heat sheild from exhaust manifond( this is tricky i tried this before, find someone with small hands and use a wrench, a tourch wrench wont work for some screws, theres not enough room to get it in there....youl see) BE SURE TO SOAK the nuts with wd40 before attempting to remove them from the manifold.
4. Remove the exhaust manifold nuts( there should be 9...4 on top...3 on the bottom...1 on each side) and detach the header from the cylinder head.
Thats all it says....now for the insall of the new one...
Installation
1. Discard the old gasket and use a scraper Paint scraper will do the job) to clean the gasket mating surfaces on the manifold and cylinder head. Then clean the surface with a rag soaked in lacquer thinner or acetone( if your a smoker, put the butt out at this time):smoker:
2. Place the exhaust manifold in position on the cylinder head and install the nuts( make sure the new gasket is in position). Starting at the center, tighten the nuts in a criss cross pattern to the torque listed in this chapters specifications, which for your car is 61 ft-lbs. Dont ask me how you can measure this i got no clue????? and there is no one here i could ask so before you start figure this part out...
3. The remainder is the reverse of the istallation.
Ok once your done make sure you check for exaust leaks!!!
This book say nothong about the 02 sensor, but (please correct me if im wrong) i dont think it will cause a problem.
I hope this helps you GOOD LUCK AND HAVE FUN and dont hold me responsible if something goes wrong
And let me know how it goes, i plan to equip a header in the near future.