Know anything about Garage Band??

Ok, so my sister just recently bought a mac laptop and included on it is a program called "Garage Band." I'm sure some of you have heard of it, or maybe you haven't, who knows? Anyway, we're trying to figure out what kind of software and plug-ins we need so I can record my songs on it and put it onto a c.d. without having to go to a recording studio and spending $30 or more dollars an hour to do it, and to where it sounds professional enough to send to recording studios. Our questions are: Can you buy the software and download it offline and straight to your computer? If so, does it work on PC's? What kind of plug-ins or other software do we need to create somewhat professional recordings of my songs? I think that's all the questions we had, so if any of you have answers to anyone of these questions or any suggestions, we would greatly appreciate your help & advice!

Also, I'm sorry I've been such a slacker on posting the new happenings in our lives, I just haven't had anytime at all lately, but as soon as I do get some time, I'll post it! I hope everyone is doing well and enjoying their Summer. And for those of you who are in the valley, I hope you're not suffering too much down in H-E-double hockey sticks! pardon my French. jk! :)