Sorry to laugh but - what a problem! The clock needs its hands washed... How on earth do they get dirty? ;-)
Did you get all four screws (the two at each end?) As Maxximilian says, it's just a matter of technique after that... almost massaging it with your hands.
You will find, as you pull it out, that the shortest item is not the wiring but the pipe that goes to the economy meter (presumably next to your clock). This requires careful but firm 'teasing' - try winding it around a finger and levering against your knuckle. Seriously! I know how frustrating it can be to not be able to pull something off/apart having gone to all that trouble.
With the instrument panel out, there are a number of small black screws to remove the instruments from the black surround. A couple near the top (I think) and a number along the bottom. Some are 'disguised'. Be VERY careful pulling the black surround plastic away, as there may always be a screw or two that you missed!
Sometimes the gauges themselves have to come off in a particular order, e.g. you might have to remove the econometer first. Or, of course, you could just clean it in situ. Try washing-up liquid/water and cottonbuds I guess? Then try meths, finally isopropyl alcohol, I'm guessing that really what has happened is that the paint has faded. Correction fluid pen? The panel 'red' tends to fade as well. Not sure if it's worth fixing that. ;-)
-Alex