The "hissing" noise that you're hearing from the power steering is normal when turning. That's merely the fluid (under pressure) dumping over the pressure relief. However, if it's constantly "hissing" all of the time, even when driving in a straight line on the highway, then you need to have that checked out.
A "gurgling" sound in the power steering might be an indication of air in the system (which should be bleeding itself out). Air in a hydraulic system is not good and could cause your pump (and drive motor on your cooling fan) to cavitate. You definitly don't want that.