CAD Addict has a solution to many of the models found in 3D Warehouse which have all of their edges showing, including parts of the geometry that should be hidden.  But having to change every single edge by hand is frustrating and time consuming.

For objects without groups or components, try switching to Wireframe view (icon shown above), then highlight everything, and right-click to Hide.  That’s it! If you do have nested groups, or components one inside the other, one has to go inside of each group/component to have this trick work.

The alternative way is to use thomthom’s Selection Toys.  One of the tools will allow you to isolate the linework from the faces so you can just hide the lines.  Once the plugin is loaded and activated, window across all the entities to be changed, right-click and go to Select Only, then Edges.  Then right-click to Hide them.

Another way to deal with it for the entire model is to change the active Style.  Go to the Style window, highlight the current Style, then click on the Edit tab, then deselect Edges.  This way you can prep your model to become a final graphic without dealing with each line in the model.

Regardless of how you get there, you will have a better looking model.