Frustrated!!

I went to the apple store today and does no one that works know anything about pc issues. No everyone with an iPhone has a **** Mac. Anyway my dilemma is I have three pc's that I want to combine the three into the newest one. I know I need to transfer my libraries from the two to the one I want to use but how do you combine the two libraries? And how do I go about synching all my apple devices to the new PCM without loosing what data is on them?