Key letters to Amazing Grace?  

Hello all you piano players and keyboard players... I need a little help. I am trying to learn to play Amazing Grace... Now I won't know how to do the chord changes.. I only know the C chord and the G7 chord and that is it right now. I don't have any music for it... and I couldn't read it if I had the notes, but I do know my hand placements and the key letters.. so if someone can give me the key letters I would appreciate it. Forget the chords right now.. If you want to add the chords fine, but I don't know how to change up with other chords than I just told you about.

If you have a really good FREE site I can go to that I can learn more on. The I have gone as far as I can with the free lessons I have already learned.

I was trying to pick it out by ear and the first line I got was: G G C C E E E C C A G ... it sounded right.. was I right? I've been picking at the 2nd line but haven't got the letters all down on it yet. I would like to learn the whole song.

Thank you all in advance.