I have a nissan beater that I drive. I need to replace a pipe that is pressed in to the manifold. I enclosed a picture. How would you guys remove the pipe? Do you need a tool to remove it or do you just pound the hell out of it? Thanks

Please ignore the arrow that is pointing on the little pipe. It is the whole pipe that I have to replace and it is sort of encircled. thanks

 

Little hard to tell from just a picture.
I assume it is leaking something.
If it ain't don't mess with it.
I find that trying to do something that looks simple sometimes turn into a more involved job that I'd like (especially if it's car I'd rather not spend a lot of time on).
If it is just pressed in from the outside, grabbing it with visegrips and pounding the pliers with a big hammer might do it.
If it is pressed from the inside with an inside flange, you have to take it all apart to get to the inside.
In many cases you are better off putting a rubber sleeve on the pipe or re-sealing it somehow (easier and takes less time).

 

You can get it out, but getting something back in will require drill / tap. As you can see in the photo, I pulled three different pipes out of my SC and replaced them with fittings. I grabbed (crushed) them with a pair of vice grips and then used a prybar to work them out, prying against the tip of the jaws.