First of all, stop thinking like a Windows user when naming your computer. Add spaces and apostrophes and funny characters just because you can.
Second of all, this happens when your computer sees another identically-named computer on the network. Somehow your computer thinks it's seeing another computer with the same name, so it says "Whoops, this might be a problem, I'll just add a number to my name to avoid confusion."
Third of all, to change it, just go to System Preferences and then Sharing.
