The purchase of a fungen or scope would be too much. Unless you know you are going to use them for other hobbies.
This would not be an easy thing to write a DIY on. Plus when I'm finsihed I calibrate the cluster. I have equipment that calibrates the cluster and updates the data prom in the cluster. I'm not sure how you would do that??
As for your issues.
1 works except the background lights
When you move the dimming sliding up and down, do the odometer and clock displays work?
If so, then the two bulbs along the top of the cluster are dead. Very common. These are the 2 watt bulbs that get hot and melt their own casing.
And 1 only the odometer and tach work
No Temp or fuel.. no speedo needle? Only the tach needle works?
This happened to me two years ago , itīs simply to solve , is just the little motor of the tach or speedo , is
faulty , and when one doesnīt work the other one doesnīt either . Normally when you start the car ( engine cold ) both works , but when you start the car and the engine is warmed up , it wont .
Just go the a cluster specialist , and it will be solved in an hour ! Itīs more work to remove the cluster than replacing this little motors that drives the needles of the tach and speedo .