Easy, easy, easy to change.
I've heard Mr. Gasket makes a good thermostat. I personally have a JET thermostat, and am sorta pleased with it. Don't get a cheap Autozone thermostat or you'll regret it.
You'll need to lower the coolant level below the line of the lower intake. Might as well do a full flush if you're up to it. There are two bolts which hold the thermostat housing on. Remove the two bolts, and you're there! Be sure you use a quality gasket, or put a ring of RTV around the housing before you re-attach it.
Get a 180 degree. 160 is too cold, and you'll lose fuel economy.