No - you don't need to learn CSS. CSS is now the meat and butter to HTML 5.0 scripting language and is what you see in wordpress editor "text" option.
Although you can edit the CSS in wordpress through your dashboard>appearance>editor - stay out of there unless you are an experience programer. I am and I stay will clear of it. the slightest error you make in the edit, will screw up your wordpress and you most likely will have to reinstall the whole thing from scratch.
And their is no real reason to use Child theme but what we use wordpress for. If you are designing your own themes with Artisteer, then you can do almost anything you like within Artisteer.
Also Note and this is a BIG NOTE - all your changes or editor to the CSS files will be lost anytime wordpress has an update. I also think this applies the your child's - but not sure on that. Again though, if you are using Artisteer, you don't need to worry about child themes.