I was trying to replace an image in my UV image editor, but the image defaults to a different image. how do I fix this?
Your image is packed, replacing it is not possible (in newer blender this option is now grayed out in this case). You have to unpack it first, if you want to replace it.
Ok, so to fix that you need to unpack the image. To unpack the image, next to the image tab (the one when you click on it it has the greyed out replace image) there's skin.png right? Next to that there's a 3, an F, a +, and this wierd thing i can't describe. Click on that weird thing i can't describe (lol) and click "Use file from current directory (create when necessary) BOOM! You can now click on replace image