im new to gimp but i need help. i dont know how to like replace an eye with another eye

lol; you beat me to it, Wallace.

That said, you can copy/paste the eye and do some clone/heal brush work to clean things up as needed. Many other ways too available such as using G'MIC and seamless blending.

That's right. using Gimp, you gimp it.

Seamless blending is great for adding in extras.

well, everyone makes typo's
i spelled your name wrong the last time Wallace
sorry

bad kitsune, bad kitsune
go shame your self

Have you done what you wanted or do you want to put your pictures here...
Someone can do them for you and even attach the xcf if you want to see how it is done.

Is it the whole eye you want to replace or just change the color? Gimp has nice color tools to do that. This one was done by selecting the colored area of the eye using the paths tool . For information about creating paths: http://docs.gimp.org/2.8/en/gimp-using-paths.html
After creating your path, go to Select/To Path to save the path. See picture below.


Now would be a good time duplicate the layer two or three times so you have some pictures of the original eye.

Then Colors/Color Balance. Move the sliders to see what they do to the colors. Below are two examples of color changes. The bottom image is the original color.

You can shop your photos using GIMP.

A great way to get a very close color match like the skin color around the eye is to use the Colors>curves tool.