Do you mean the "service" light, or the "check engine" light?

The service light, which comes on at 5,000 mile intervals, can be reset by removing a small rubber plug from the instrument panel cover (near the speedometer), and pushing the button with a slender instrument, as noted in one of the other responses. Older models (pre '88?)required reaching up behind the instrument panel to push a button on the back of the speedometer.

If it's actually the check engine light, it can be reset quite easily by pulling out and re-inserting the number one fuse. This circuit runs the fuel injection pump and the ECU. Since there's no battery in the ECU (unlike your home computer), any fault codes are erased until the ECU detects them again.