so my dashboard lights and right brake light went out all at the same time

These early 220 chassis s classes had an issue with the intrument cluster going bad. It was covered under an extended warranty for a while but I'd imagine that time has long passed. Contact your dealer with VIN just incase. The radio would ask for a code if the battery went dead. Brakes light operatin sounds normal. You press the brake and they turn on, you let off and they turn off. You may have a bulb or two out though. Alex

Sorry didn't see the year right away. This is a 140 chassis. Everything applies except the intrument cluster. That will require hands on electrical testing. There was no common issue with the 96 and clusters. Alex