The right side where the leaves look normal and green are converted to polygons. But before they are converted to polygons, the leaves look pink and white as shown on the left side of the tree. I can't figure out what is causing this!
My second problem is: When I render my scene, the background looks totally skewed! When compared to the unrendered picture, it has choppy black lines that I have no idea where they come from..
paintfx in maya and done at render time, that's why you can't see them in the viewport, once you make them polys, the become, planes with texture and that's why you can clearly see them in the viewport
your second issue might be the uvs, or you have double geometry in the same place, if now check the UVs, or just try with a default NURBS sphere