What should I do?

If I were the seller, I would have sent updated pics of the dash once I found the rot. Based on the first pics, I don't think it would be unreasonable for the OP to expect to deal with a little surface rust and cleaning. If he were complaining that the gauges and/or switches didn't work, well the O/P would be on his own since the seller made no claim of operating condition. No way would I have sent that without touching base. But that's me.