1. Sound card if you are aiming for anything nearing professional , check the forums here for good soundcard advice.
2. the software you need rather depends on what your going to be doing, are you actually creating the tracks or just chopping pre-recorded segs together?
3. mic, Gearslutz.com has a good forum and I reckon someone on there would have a good perspective on mics for pc usage re: professional level music.
But like everything else, you get what you pay for, and as a singer, your mic is your link to the pc, skimp here and no software is going to help you sound ok, but here a Gearslutz link to the pc section, hope this helps in some way man http://www.gearslutz.com/board/music-computers/