MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
I print them sitting on their tracks, which ensures that the gun barrel prints nicely and strong. (That's why the gun barrels are drawn with a flat underside - too small to be obtrusive, but gives a lot more surface area during printing.)
Support is required. This is automatic in the UP software, so I'm afraid I can't help with that.
0.15mm or 0.2mm z axis layers should work fine.
If printed in the suggested-above orientation, all features are designed to be big enough to print.