Re: rpm guage
Both of those gauges require +12 volts when the key is on. They also require a ground connection. The only connection between the gauge and the engine is the temp sender for the temp gauge and the send wire for the tach. I suspect either the +12 volts or ground connection has come undone. Gauges are daisy chained meaning +12 volts and ground connects from one gauge to the next so if one has become disconnected, the next gauges in line will not work -- sort of like your Christmas tree lights.
