Yeah so i got stuck at step 4 cuz i don't have any Executable Jar file named "Minecraft" . Instead i have a folder named Versions and in it i have "1.6.4", 1.6.2, and 1.5.2 and usually i install mods and stuff into that so i don't get what to do...even if i open those files it doesn't have "mobs" or "char" in it
open the version you use in 7-zip or winzip, go to assets, minecraft, textures, entity and scroll down until you find "steve.png"
rename your skin "steve" and replace it with the original steve skin (if you want to keep it, save it somewhere else so you can set it back whenever you want using the same method)
Go into versions, open the folder and you SHOULD see the executable .jar file. Then, open it with 7-zip or WinRar and look for "assets", then "minecraft", then open "entities" and and look for either char.png or steve.png. Replace the file, and you are done. (Keep in mind, though, I did this with 1.7.10, but I think it should work with 1.6.4)