<< Can MoI SKP output work directly with the Twilight 2 render program? Or must you first bring the SKP into Sketchup?

Twilight2 is not a stand alone (it's a plugin's Sketchup) so Yes you must input your SKP model inside Sketchup before! (works fine with the free version of Sketchup)

PS A little trick : if your Moi model is not a "single part" model, better export it in 3DS format from Moi to Sketchup (Menu File / Import...3DS)
then explode it so you will have each part as component!