Take the cluster out and look at the back of it. There are about 12 long philips head screws that hold the sections together. Remove them and you can clean the inside of the clear plastic, faces of the gauges etc. It's not difficult, but it is time consuming to do. Make sure you have a good quality brand name #2 philips, in good condition (no wear on the tip) as the screw heads are soft, and prone to rounding out. The printed circuit foil is fragile, so be extra careful not to damage anything. Most of the screws that hold it together do not go through the foil. they are around the edges and the ones in the middle are in large holes in the foil, so that they are in direct contact with the white plastic. There are other screws that go through the foil, and make the connections to the actual gauges. You do not want to remove these---it is not necessary to do so to take the face off of the cluster. You want to remove all the big ones around the perimeter, and a couple in the middle, if I remember correctly. Also the two that hold the lighting rheostat to the cluster.

It's been a while since I took mine apart, but I think there is detailed information in the FAQ.