2000 GMC Savana van gauges acting weird


I just bought a 2000 GMC Savana van. A few of the gauges are acting weird. The fuel is vibrating fast at the full mark. The oil pressure is jumping between 20 and 40 but not smoothly like it should and under a steady throttle it shouldn’t. And the last is the water temp doesn’t work at all.

Any ideas?? I’m thinking maybe the odometer display is bad.