If you don't want to download WinRar or 7zip, you can also do this for step 7:
Make sure your system is showing the file type (Example: WoM.exe, not WoM.)
Right click on your minecraft.jar
Click change name
Change the .jar to a .zip and click OK
Then go into it,
Do what you need to do,
DELETE THE META-INF IF YOU INSTALL MODS (unless otherwise stated)
Rename minecraft.zip to minecraft.jar
And there you have it
Thats just what I did before I got WinRar, which I still find clunky and annoying, so I still sometimes just go back to zips.
Hope this helps!
PS. If you start Minecraft and get a black screen, you probably left your minecraft.jar as a zip.