If you can remove it any at all the plastic screw is gone. Sometimes the metal bracket the screw is connected to is gone as well. If you were barreling down the road in some third world country you might need the screws to hold the instruments in but on smooth roads the rubber ribbed gasket is really all you need.

Pull the pod out far enough to reach the speedo cable and unscrew it. It turns counter-clockwise. Just let it drop back as it will not fall away too far. There will then be an electrical plug or two which may or may not be difficult to pull off and then there is the oil pressure line that is screwed into the back of the oil pressure gauge that will need to be unscrewed. Watch out here as there is normally some very slight loss of oil. Put a rag or paper towel under the pod to catch the few drops of oil that will come out.

You should then be able to pull the pod out to where you can reach the light adjuster. You will not be able to pull the pod all the way out since the temp gauge might be connected to the temp sensor via a thermocouple (some are and some are not. It s a silver threaded looking line if your car has one.)

The adjuster is normally held in by a screw or two which are easily removed. If there are wires to it they will come off as well. Then it just pulls right out of the back.