On the driver's side of the engine under the timing belt cover. It is driven by the the timing belt. If you do change it you should always replace your timing belt and water pump while you are in there. You will save yourself time and money in the long run.
Of course it is possible but why would you want to do that? You have to remove the cam belt in order to replace the water pump. Once you have the belt removed you could just reinstall the old belt but would it not make good sense to replace it with a new one.
You do not have to replace the timing belt but you will have to remove it in order the replace the pump. Unless the belt is pretty new I suggest you replace it at the same time you replace the pump. The pump should have been replaced when you replaced the belt at 105,000 miles.