There are several programs (some shareware, some paid) that can "listen" to a song and give you a spectral display. The one called Transcribe! is the one I like. It lines up the display with a piano keyboard so you can see the music spikes and assign a note to it. Right clicking on the piano note also shows you the guitar fret equivalent.
It won't do everything for you. You basically open a file and listen to it while the spectrum analyzer does the display. Freeze or loop the part you want to work on and it'll show you the notes associated with that particular moment in time.