They don't need to know how git works, they need to know how to use it.
Just like I don't need to know the details of an internal combustion engine to drive a car, someone who only does CSS work doesn't need to know how git works to push commits. A simple GUI interface suffices there.
The problem is that the official Git GUI interface is unbelievably bad and happily lets you put yourself into situations that the GUI is completely incapable of getting out of. A default GUI that can't essentially softlock itself would be fine for most casual users.
There absolutely does. It's called Git GUI. It's right here: https://github.com/git/git/tree/master/git-gui
But, hey, git is sooooo superior. </s>
GitHub has done almost as much damage to version control as PowerPoint has done damage to presentations.
Of course you won't be able to do it in a couple of hours. Most people spend years learning the things that are required to understand how git works, or at least many months if you want to learn in a fast, intensive manner.