Regarding the "service" light, going out after a few minutes is perfectly normal; there are no codes associated with it (there's nothing wrong), and it goes out because it's just a reminder, and I suppose the designers didn't want to make it too annoying. It will keep going on when you restart the car until you press the reset button.

The reset button is (at least on my '93) a little "dimple" in the lower right hand corner of the instrument panel. You need to take a very stiff, narrow tool (like a small size hex wrench) and push it into that dimple hard(!) and deep (at least one half inch) -- you'll feel a little resistance at first, and then it will plunge the rest of the way.
Then, when you restart the car, the light will come on briefly and then go out (and stay off) after driving a couple of hundred feet.

Don't confuse this with the "check engine" light,