92 Sedan Deville digital dash

Start at the underhood power center. Check all fuses with a test light and be sure all main power relays are turning on

I have fixed quite a few of these and what usually happens is the climate control module goes out, that causes a short that fries the body control module. IF this problem just started, Unplug the climate control module and the dash should light back up. If it does you only need to replace the climate control unit. Leave it unplugged until you get the new one to prevent frying your body control module (bcm). If the dash doesnt light back up, you will need the climate control unit and the body control module located behind the glove box. The body control module is about $99 at napa autoparts, and Oreilly autoparts. The climate control can be found used on ebay relatively cheap. Hope this helps you and many others out! This is a problem that has plagued these cars for years. Sometimes just replacing the body control module will temporarily fix the problem, but if you dont get to the bottom of what caused it to fry in the first place (in this case the climate control module) you will just be replacing it again in the future.
Other possible culprits can be the fuel data center,and the digital dash itself, but from my experience, and from the description you give with your a/c acting up, ill bet its the climate control.