Help Beginner questions about replacing model

So i downloaded a adawong nude mod and then exrtacted model and add a cloth on model. Now i extracted model back as a mesh file using script but when i play the game my dress doesnt seem to appear ada model is still nude.

So my question is which file should i rename my added cloth as?? I mean there are 5 LOD groups. How do i determine which LOD is used during gameplay??

Also during the exporting process do i need to select all objects in the scene or just the outfit that i added ??

Bec when i select all objects in scene to export i get error No function or Undefined