If you just need a saber hilt and blade color replacements, there are plenty of them here. But if you really mean to do some modding, for starters, you'll need.
Kotor tool to extract game source files (.mdl mesh files and .tga textures)
Mdlops to convert extracted .mdl files to readable ascii format
Gmax/3D Max and NWMAX plugin or Blender (though I haven't tried using Blender) to import said ascii .mdl models and do some modeling/tweaking
Various image editing programs (Photoshop, Gimp, etc) to edit .tga textures
As for tutorial, you can start from here: http://deadlystream.com/forum/topic/114-how-to-start-modding-kotor/
and here https://web.archive.org/web/20160210162357/http://lucasforums.com/forumdisplay.php?f=592
Good luck