Now that TT ha provided the schematic, we need to know a couple more things. It would appear as if the rheostat shown on the left hand side about 3/4 of the way down the page is what controls the dash lighting. It has the yellow and grey wires going to it. Set the dash brightness that you desire, then remove one of the wires. Measure the resistance across the two terminals on the switch. (You may or may not get an accurate reading without removing a wire.)
Then, measure the amount of current by connecting an amp meter between the wire that you removed, and the terminal where it was connected. The first part will indicated the what wattage resistor iresistance needed, and the second part is for determining the wattage.
Black 2000 SSEi, Silverstar Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, drilled 180 degree thermostat, Intense FWI, PCM, shift kit, and 3.4 Pulley. Solid front mount.