Thanks very much Deano!
Here are some pics of the dash taken apart. It's not sealed at all, it just snaps together. If you spray water thru the screen (by your knees) into the battery area, moisture rises from the battery area and condenses on the 'glass'. Mine was manufactured 10/06 and has some tape covering the lower seam. You could remove the instrument cluster tape all of the seams, which would reduce the amount of moisture that gets inside. There are two breathing holes at the bottom with permeable fabric covering them.
There are no 'clips' holding the instrument cluster in, it just presses down into the dash bezel and is retained by friction. If you didn't want to stick a screwdriver in, maybe it can be pushed up from below (above the battery). I did not try this but it looks like you could remove the screen (by your knees) and stick your hand up there and push it out from the underside.
I took it all apart and cleaned the dust off the dash faces, then used silicone to glue the 'glass' back on. It looks new again. I was a little suprised how cheaply the instrument cluster is made, it looks like it ought to cost about $5. It's made in USA by Maxima Technologies.