As far as speedo is concerned, (assuming yours is not gearbox driven) , it receives its pulses from a sensor mounted on the inside of the front driver-side brake disc. This is a quite delicate device being essentially a hollow bolt with electronics potted in. It is easily broken off when for instance you wipe away excess grease. With the car jacked up, if you spin the front wheel you should see a tiny pulsing led light when peering into the end of the device. I think Dave W posted on here a year or two ago about replacing the sensor, as there is a specified clearance to be set between the sensor and the bolt head that whizzes by to trigger the pulse.
If you really want to remove the dashboard, as well as the three main screws, you also need to remove the tiny ones underneath that hold the dash to the undertray.
Empty the glove box. Lower the steering wheel. Place some padding across the steering wheel and pull the dash towards you and rotate the top towards you as it comes out.
BEWARE: it is very easy for connectors to become unplugged as you pul it forwards so double check everything is intact before re installing. (The wiring behind my dash was akin to the proverbial rat’s nest...but installed by craftsmen, naturally.)
