weird issue with repaired STL not seeing a part

Your model has a few shells with the faces reversed (facing inward.  This results in a shell with negative volume.

Open up the model in Netfabb, select it, then click the repair button.  You'll see that some of the parts are in red.  Those are th e parts with negative volume.  On the right click Select Shells with Negative Volume, then click the flip selected triangles button.  This will reverse the triangles and fix the shells. 

There are a few other places where the triangles are flipped (red) so you might want to fix those as well.  Once you're done, click Apply repair, remove Old part =Yes, and export your fixed model.

I tried to fix most of the errors in this model, but they're simply too many.  There are almost 10,000 intersecting triangles.  I think this model was made in 3D Studio Max or something similar, as there are also many open faces, which are almost impossible to close.

I did manage to clean quite a bit up, and, although Slic3r still can't properly slice this, Cura can, so try that.

I tried to upload the model here, but even zipped, it's too large, so I uploaded it to a hosted site.  The link is below:

https://1fichier.com/?tkmb8fx28o

Good luck

Post a pic of the model when you finished printing

pics show both sides of b4 and after prints, right one that has become 2 parts in b4 last repair. still have hollow place under driver door where red panel by running board still needs fixed. also the top sign board is messing up due to fast layer builds not being cooled in between. and shelves are very thin making clean up of support near impossible. but making great progress.