how do i remove the stock manifold? first steps, and tools required? civic 96 EX

 

Some PB Blaster would help free up the bolts, first off. You're going to need to unclip the o2 sensor, which is just a wire going into the passenger-side.

There's 3 bolts holding on the aluminum heat shield, I believe they're 12 mm. Use a socket set to remove those, and slip the o2 sensor wire through. After that, there's a bunch of bolts on the (now brown) exhaust manifold.

PB Blaster the crap out of it for a while, with the car cold (otherwise a bit of smoke will occur), as well as the bolts going to the down pipe. (Spray downward.)

I'm pretty sure the bolts holding the manifold to the block are 10 mm, but I could be mistaken. For the down pipe, you may need a socket extension in order to reach, and *unconfirmed again* I believe those bolts are 14 mm headed.

Be sure to replace the gasket if necessary when you re-install everything. Loud leaky exhaust sounds and smells bad. :-)

Also, it's almost guaranteed that this information has been posted before.

 

It's easier to drop the manifold and downpipe together and separate them afterwards. You have to jack up the car but it'll usually be faster than trying to unbolt the dp from the manny from the top, especially if you are worried about rusted together bolts.