This has been discussed so many times: you are not missing ANY objects. The objects are there, just some parts are invisible. And when only some parts are visible, the problem doesn't have anything to do with GSX or the installation, since we clearly don't distribute "partial" objects.
What's really happening, it's a problem with video settings, and the most common cause for this is a problem with shaders, so you can try to rebuild them by removing this folder:
%LOCALAPPDATA%\Lockheed Martin\Prepar3d V4\Shaders
On the next start, the sim will run with a black screen for a while, then everything should come up again.
If that doesn't fix it, another common cause for missing parts is having updated P3D to 4.4 or 4.5 ( which are the only versions supported by GSX right now ), using the Client only. This won't work, so you must update the Content too, or use the P3D Full installer.