Once you have permission,
* Open the .scn or model.gmt in Simed,
* Right click on the object you want to extract and select 'Edit (object name)'
* When the dialogue pops up, click 'Isolate'.
* Then up on the menubar click 'Edit' and in the 'Transforms' section click 'Center Model'.
* Then back in the menu bar click 'Export', click on '.3ds' and export to a directory.
* Then, export textures to the same dir as you exported the 3ds. (this is crucial, without the tex. in the same directory, XPacker wont be able to import the textures.)
From there you can import it into XPacker.