Several things to try:
> The Body Control Module (BCM) controls the instruments. You can reset the BCM by removing the IOD fuse in the fuse box (PDC) next to the battery for 2-3 minutes. If this fixes it but, the gauges keep dying, you may need a new BCM.
> According to a power distribution schematic, if you are not having transmission problems and your rear wipers work, the instrument cluster fuses are good. This also means the instruments should be getting power (back lighting is powered seperately). Try an instrument cluster self test. See the first link. If it's getting power and the cluster is good it should cycle through the test.
> Try the dash bash test. Smack the dash above the cluster and see if anything comes back to life. If it does it indicates you may have cold or cracked solder joints on the instrument cluster circuit board, specifically where the connector is soldered to the circuit board. Could be the case even if nothing happens when you smack the dash. See second link for the fix.
http://forum.chryslerminivan.net/showthread.php?t=10110
http://photoshow.comcast.net/rlshaull/