Android Noob: Cyanogenmod on the Samsung Galaxy S3. Is it worth it? Anyone have CM10 on a S3?

I'm a complete Android noob, moving from 3 years of iOS on an iPod touch and 1 year of Windows Phone 7. I know nothing on Android. I know what a root is, but I don't know how it's achieved. I know people talk about stock roms for non-Nexus devices, but I don't know any, apart from Cyanogenmod, which I only know the name of.

So my question is this: Is it worth installing CM10 on the S3? I have a i9300 (international) model. If you have CM10 and a S3, how's battery life? How's speed? How is it overall. Is it worth it if the only thing I like from TouchWiz is the rotation lock? And is CM10 stock Android, or is CM something else?

Also, how would I be able to do this? What software do I need to use? Will it be possible to restore TouchWiz, like I just got the phone out of the box? And can I move all my apps over, or will they disappear into thin air (I sync with Google, but as a noob, I don't know how well sync works).

If you can answer any of my (many, many) questions it would be greatly appreciated.