FSX Gmax Gamepack file

Hello,I am interested in making some planes for FSX. I have some questions-I cannot export to MDL or CLD after saving the file and re-opening it. Is there any solution for this?How do you make textures for a model? How can you make seperate textures for each side of the plane?Are there any three-views available that match the specifications of the real plane? (length, height, width etc.)