I've been playing Stairway to heaven over and over again, and it seems now that as much as you play a song, the easier it gets to sing and play. I'm no singer, and being that i've only been playing for a year, i can see that it shouldnt be that hard after a long time of playing the same song.

And to capitalize on another's quote, Purple Haze is very easy to sing and play, it's a good starter