Had more time to think about this. Did some mods to wife's People GTi300 and made a discovery that may help: Unplugged the fuel sensor to remove the rear "tupperware" and noticed on a test of the mod the fuel gage on the panel was not there! This leads me to believe you may have connectivity problems with both the fuel level sensor and the temp sensor. This leads me back to "unplug, goober, plug back in" recommendation.
Karl
PS: Just re-read the whole thread. Sklnzl, you said the whole display went blank, right? Was the backlight still on?