Most importantly: whichever version (Emacs or XEmacs) you end up using has a tutorial. The startup screen (when you start (X)Emacs specifying no file(s) to edit) tells you to try <samp>C-h t</samp> ("control-h, then t") to enter a tutorial.

It's certainly old-fashioned (it won't even assume you have arrow keys on your keyboard), but it will teach you the basics of text editing on (X)Emacs.

After that, the serious documentation lives mostly in info (<samp>C-h i</samp>); learn to use info, and you should be well on your way...