Ok, I can't do it now, but I'll pm it to you later. Glad I decided to ask.
Okay it was just as I remembered. Overlapping faces cause those darker areas. Except your model is fine. If you zoom in further you can see that the dark areas disappear. The reason they appear further away is due to floating point errors in Blender OpenGL rendering. Nothing to worry about. It's completely normal and to be expected.
I also noticed that you have quite a bit of unnecessary geometry and features too small to notice. For example: the tiny edge rim in the indent where the wheels go, the tiny square in all corners of the side windows, and the faces in front of the bus below the window. There's no reason for there to be more than 1 quad and 2 triangles. You have similar problems elsewhere in the mesh. You can use triangles. It helps cut down face counts.
There are a couple of holes in the mesh as well. If you zoom in very close to the edge of the big side window you can see that it doesn't actually connect to the rest of the bus. It doesn't
really matter since it's probably too small to see in-game but it's still good practice to always avoid things like this.
You should also fix your normals. Press Alt Z and notice how there are holes in the mesh. Read this:
http://forum.blockland.us/index.php?topic=157886.0#post_fixing It's old but the things still apply.
How would I fix the normals on an object with no thickness. Should I even do doing that, or should I give all objects thickness? My issues are with the wings and the netting around the balloon.
Same wing, only one side can have the drawn normal pointing away from it.
Unless you enable the Double Sided option (visible in the screenshots) on that wing object. Make sure the 2D wings are the only things in the object when you enable it. I also wouldn't hurt to make sure all the normals are facing the same general direction on those wings. What it does is it makes the game engine render a face on both sides of all faces, essentially doubling the triangle count. This is why you should always have it disable except in situations just like this.
