should have got the 3.8. the cruise control could be a bunch of things like the 3rd brake light being out, abs issues or it could be out of adjustment. the heater blowing cold could be a blend door actuator. the oil capacity is like 5 quarts, and adding oil when the oil light on was a good idea, but it probably could have taken 2 quarts when it is low enough for the light to come on. sounds like you fixed your overheating issue. the headlights pretty much always stay on.