It's much easier to use a simple text editor like Notepad or Wordpad to edit CFG files. Adding textures should not affect the performance of the aircraft in any way. Make sure you add the new entries correctly & don't delete/remove existing default entries. This tute should help. http://www.simviation.com/lair/Repaint2002.htm

The folder names do not need to be numbered like the defaults (Texture.3 etc) but can be anything suitable like Texture.blue, Texture.green & so on as long as this is defined in the new CFG entry.
For example, texture=green