how do i edit the jar file?

[sk8champ0]

I wanted to change the default skin inside the jar file for my brothers because they see me as default steve and i have a skin on my character...  This is a very stupid bug in single-multiplayer that is still not fixed by mojang as of minecraft 1.7.10. And every time i change the steve.png file it reverts it back to default. I tried to make the folder 1.7.10 or the file steve.png read only, but then minecraft forge wont start.. why the heck cant i just change such a simple thing and is there a way to change it?

[LexManos]

This is pretty much the exact reason resource packs exist... seriously....

[sk8champ0]

thanks i forgot you can do that with resource packs.