Head lights are very dim on my 1998 Pontiac Grand Prix

You might have a bad light bulb or your ground connection is corroded and needs to be cleaned. Check the bulb if it is faded in color, replace that, if it looks fine then check the ground connection. If that is corroded then clean it and apply some dielectric grease to slow any corrosion back.

Also check to make sure your battery and alternator are putting out the proper voltage.

a voltmeter used at the connector can read the volts applied in the circuit and verify ground. a voltmeter can be found easy at a parts or tool store. readings that differ from battery voltage show voltage drop exists. Lenses that are discolored can be restored with a buffing pad set from the same two stores.

a crusted mess at the battery can be cleaned up with baking soda and water before electrical repair.