Pink Floyd, Van Morrison, Eric Clapton?

I auditioned for a band on friday. i sang paper bag by fiona apple. they really loved my voice and they want to get me started with them... they told me to learn moon dance by van morrison, brain damaged by pink floyd (which im having a really hard time with), and i shot the sheriff (eric clapton version)...i am a 21 yr old female and im having a really hard time learning the right notes to start singing for these songs. i know that even if im singing my best i could never stand up to the originals, but i still want to take advantage of an amazing opportunity. Any advice on how or where i can find help on being a female covering these songs? Ive barely even found female covers on youtube.. thanks