New head unit for '07 chevy cobalt?

I've been looknig around and can't seem to find info on puting in a new head unit for an 07 cobalt. Everywhere I looks it sounds like there isn't a proper wire harness to do it, anyone know anything about it? I also can't find (and this was just in a trip to walmart i'll have to look around some more) a mounting kit for an 07 cobalt. if anyone has any extra info that'd be great, also what are some places I can go to have it installed? I can do it myself, but since its a newer car I don't wanna risk breaking anything.