A few questions about Blender and textures...

For the past month or so, I've been working on my VW Golf project. Unfortunately, my complete lack of experience with Blender has made that rather difficult. I'm trying to work with textures and materials right now, but I've stumbled across a few issues. If anyone can help, I'd really appreciate it.
1. Whenever I launch Blender and import my current model, the lighting seems weird. From one angle, the wheels look perfectly white. From the opposite side, the entire model is black. Here's what it looks like:

Here's what it normally looks like:



2. This issue has randomly appeared. Whenever the glass on the windows or lights breaks, it turns yellow. This isn't the "no texture" orange color either. It turns bright yellow. None of my current textures involve the color. I don't know if it's a glitch or a problem with my textures.


If anyone has any idea how to fix these issues, it would really help. Thanks in advance!