It depends on how much you want to test. My tester can generate all the sensor inputs, including VSS. If you simply need to verify that all your lights and LCDs are working, the initial self test that the cluster goes through when power is first applied would suffice.
Here is a cluster on my bench when power is first applied:
Here is is with simulated inputs:
The pins you'll need are all on the 32 pin connector:
This is from memory, but to get the cluster to self test, all you need to do is apply 12vDC to pins C16 and D16 and a ground to pin D1.