Okay, well, the two issues you have are unrelated. The "region in Blender" you were talking about is simply the view clipping plane; by default, it's set at 500 metres. which is too small for a ship of this size. So, go the 3D window, "View" menu, "View Properties", and under "View camera" pull "Clip end" up to the maximum of 10 000 metres. Centre your ship properly ("Center New" button in the Mesh panel) and move it back to (0,0,0).
Then, you have quite some messy geometry in there, especially around the tailfins. This seems to be what's actually causing your conversion issue. Start off with W -> Remove Doubles (Editmode); then go to edge select mode and press Ctrl-Alt-Shift-M to select messy geometry. Specifically, there are faces inside the tailfins, which you should delete; and the tip of some of the tailfins doesn't line up properly. Select the two tip vertices and merge them.
After having done this, you should be able to convert the ship.