A stout teaspoon will be sacrificed...
Use a file to sharpen the tip of the spoon to a fairly fine edge which will easily pass between the back of the bezel and the plastic body. Position the spoon so the bowl of the spoon is resting against the plastic body and gently lever the bezel outwards. Continue working around the bezel until you can see that it will pass over the plastic lip of the gauge body.
Then position the spoon as described above, push the bezel outwards and downwards over the lip in one spot. You should be able to slip the spoon tip between the bezel and the lip and lever it off the body completely.
With regard to the Volt meter... after removing the needle it will be necessary to reset the correct position of the needle so that it indicates the correct charge level ie. 13.8 - 14 volts when the car motor is idling and no accessories are in use (eg. lights headunit etc). To do this you will need to connect the gauge to its wiring in the car, and start the motor. Once it is idling you can carefully replace the needle onto it's post with the pointer aimed in the appropriate direction. Once you are satisfied that it is pointing correctly, switch off and disconnect the gauge, replace the glass front and bezel and then it will be ready to install
With regard to the Oil temp gauge , the needle needs to be replaced with the needle pointing below the stop post on the dial face, and then carefully lifted over that post. This provides exactly the correct "tension" to the needle so that when you turn on the ignition the needle doesn't indicate that the motor is already warm...
With regard to the replacement of the clock needles, you will see that the spindle protruding from the face is square shaped at the bottom to fit the shorter needle...fit the short needle so it engages correctly and then move it to the 12 'o' clock position. Next fit the longer needle also pointing at the 12 position... that will co-ordinate them both to correctly synchronise every hour...
Replacing the bezel is quite simple.
Place the bezel complete with the glass cover face down and position the gauge body onto the bezel so that one side is already located into position with the plastic lip inside the beze.
Slowly apply pressure downwards and around until the bezel clips in all round.
Lastly, use the handle of the spoon to press the somewhat lifted back edge of the bezel all the way round so it is back to where it was - or as near as dammit, since the metal will not return all the way without a proper bezel press, but it will do for your purposes of securing it enough.
Another tip.
The glass fronts of these gauges are perspex, and can be brilliantly restored with very little effort to perfect clarity and a scratchless surface. While you have the gauge front off, you can use a piece of microfiber cloth doubled over and some Brasso polish. Place the cloth on a flat clean surface, apply the Brasso to the cloth sufficiently to cover the width of the perspex diameter, and polish both front and back surfaces until they are both super polished and clear. This will take aprox 3 minutes of buffing and well worth the effort.
As you can see, I opened all the gauges, and cleaned, polished and re-painted the needles with fresh red dayglo paint. The original paint had faded to a dull orange....
careful what you wish for... 
