Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
The oil pressure switch will need a special socket, (normally found at any autozone store and it's like) and it is right next to the distributor. Being that the age of the vehicle, and milage, it would be best to do a complete tune up on it.
1. Spark plugs
2. Cap and rotor
3 Ignition wires
4. Air filter
5. PCV valve
Let me start with the oil pressure switch. Here is a picture of it and it just unscrews, (after the wire it unplugged)
INSTALLATION Special care should be taken when installing spark plugs into the cylinder head spark plug wells. Be sure the plugs do not drop into the plug wells as electrodes can be damaged. Always tighten spark plugs to the specified torque. Over tightening can cause distortion resulting in a change in the spark plug gap or a cracked porcelain insulator. When replacing the spark plug and ignition coil cables, route the cables correctly and secure them in the appropriate retainers. Failure to route the cables properly can cause the radio to reproduce ignition noise. It could cause cross ignition of the spark plugs or short circuit the cables to ground.
The cap and rotor, you just take the scerws out from the cap, (at the distributor) and the rotor just pulls off. You don't have to loosen the hold down bolt.
The igntion wires you will want to do one at a time.
The ignition timing is not adjustable and there are no mixture adjustments. You may want to just clean the throttle body with some throttle body cleaner though, (I always do)