3.8 V6 overheating

[GhettoPop]

This questions is on my dad's 93 sable w/ 3.8 V6. This car has only approx 50k miles!!! He said the water temp gauge was reading higher than usual the past day. After letting the car idle from cold to hot, I noticed that the electric fan was not turning on, even though the t-stat opened up at the right time. The radiator and overflow tank are both not low on antifreeze. The temp gauge was getting pretty high towards the red so I shut the car off. When it cooled down I let it idle again. This time the electric fan did come on, but it seemed to come on a little late (higher temp) than usual and seemed to shut off a little earlier than usual (temp did not go down as much as it should). I am unfamiliar with this engine but is my problem a temp sender or the fan switch? Please be as descriptive as you can as I do not know the location of anything and this is my dad's daily driver, thanks.