Dont fear! this just means blender does not know what directory to find the textures. You can fix this by selecting File>external data>find missing files> and select the textures folder from the downloaded zip file. 

Due to its highpoly nature, this model was not created for the intent of game usage.

Yes! The doors including the tailgate can be opened. I provided empties parented to the proper meshes, so all you need to do is rotate the empties to open the doors. 

When you purchase this model, you receive a Blend file, an FBX file, and a Collada file. Both the FBX and Collada file offer a high and lowpoly version of it for ease of editing.