Learning a song on guitar?

Hey, so I've been teaching myself the acoustic guitar for around two
months now. I've been doing pretty good but I've not been practicing
enough at all! I know alot of chords, but I'm not fast real fast at
changing from one chord to another yet. Do you think instead of
learing a song this week that I should just practice alot on my chord
changes? Also is it essential for me to learn scales? If so which
ones?
And last question do you think that if I start next week and practice
learning a song everyyday for like 3/4 hours that I will be able to
play it properly within five weeks?

Thanks for your help1 (: