I tried and opened the pink inverter as my dash was not working anymore. I opened the dash first, no signs of burns, tested the inverter, cut the pink plastic, found a snaped solder and some damaged wires of the small transformer. I'll try and come with some pics of the cleaned inverter. I did not get all the caulk off, but does the small transformer have any specs writen on it? I'm not an experienced electrician, but can solder something if I have the piece in front of me :) I can even use the same board...
PS: this is my '88 Reatta (we are the same age). It's a Ca car so absolutely no rust, I tried and fixed most of the engine/trans problems, got it up-to-date with the maintenance, fixed some electric problems (including a faulty headlight switch), but still have this dash problem that just came up and faulty headlight motors which I hope I'll fix soon...