The only thing left is the oil pressure idiot gauge (it is "supposed" to read in the middle above about 5psi) and the lights on the bottom and the gas gauge, what exactly isn't working? There are two connectors and a speedo cable on the back of the cluster, not to hard to get at, I would see if there's any corrosion anywhere as well as check all the fuses both under the dash and under the hood (passenger side in the "Power Distribution" box)
If the oil pressure gauge isn't working I wouldn't stress too much, there's an "anti slosh" module on the side of the cluster too that drives the gas gauge.
If it helps any the clusters are the same from '89 through part of '92, they switched in mid '92 and that stayed the same through '94, if junkyarding for a cluster you can tell the difference by the color of the circuit board on the back, it's been 15 years since I've had mine out I think so I don't remember what color is what...