To remove the dashboard there is a spring clamp at each end, reach under the dash and push one forward with your thumb, they're quite stiff, and it should all gradually come towards you and out. You don't have to take it all the way out to get to the instrument lights, from memory the festoon bulbs are little shorter than normal so you might have to hunt around for ones the correct length.
The photo is when I rewired mine with multi pin connectors to make it easier to remove, but it shows the two clamps and the bulb holders. No idea what the switch could be under there!
Noel