There is a command in Moi "Flip" that allows you to flip your surface normals before exporting to 3D Coat.

Unfortunately one of the problems in Moi is there is no command to view your surface normals like you can in Rhino. Maybe v4 will get such a feature, have to wait and see.

So yeh best to sort fix the normals issue in blender first, then go to 3D Coat.