2000 Dodge Stratus problem

So I get in my car and turn it on and leave to go do my errands. When the car is warmed up and I'm sitting at a light it has started idling little lower then usual and slightly more ruff. And the oil light comes on when Idling(just got an oil change though). Also when the car idles the tempurature gauge needle goes up to the half way mark. Now it doesn't normally do this and I'm wondering if this is early signs of some sort of overheating problem? Also most of the belt are really hard to get to and I cant tell if I need to replace the timing belt. I've had the car for 2 years. And I dont think the previous owner replaced it. So im wondering if its a good Idea to do it just in case. Thank you