Your issues sound like an easy fix as there are only a couple of things that can go wrong, it’s common on clusters and easy/cheap to fix.
Water temp sensor, checked by putting the plug on the wire to metal and seeing if the water temp goes all the way to hot. If it does means the sensor needs to be replaced ($30 or so). If it doesn’t then need a new diode in the gauge or replace. If it’s not moving at all then usually break in cable.
Tachometer, checked against a digital instrument, if doesn’t follow the increase in rpm with acceleration it’s the diodes, if needle jumps when you turn the ignition on it’s starting the car and whilst running reliving the needle and reposition to rpm then turn car off.
Diodes are matched at your local jay at for about $5 each and a little soldering.
I am in Brisbane and think I have a spare cluster bits that you are after - if you want to spend more but just plug and play. PM me for details.