Got your PM about this problem. It is an old thread but seems like the problems remains for a lot of people.
I actually own a '94 Altima, but I can interpret the electronic diagram for the 2000 Altima as it relates to this problem.
First off, the 2000 Altima has integrated meters and odo/trip meter in a circuit board known as the Unified Meter Control Unit (UMCU). This unit controls the speedometer, tachometer, fuel gauge, and water temperature gauge. It also receives the vehicle speed via the Vehicle Speed Sensor (VSS) and sends "a copy" of it up to the car's computer, the auto transmission controller, and the cruise control controller.
Now you mentioned that the meters suddenly drops out of action instead of it gradually dropping out. This is 90% indicative of either a power or ground problem. And since this happens intermittently it sugguests a problematic terminal connection for the power or ground somewhere that feeds the UMCU. Intermittents are not easy to locate because you have to wait for the item to fail. That is why it is not easy for anyone to locate. Some techs try wiggling the wires or using cold blast spray and it sometimes helps troubleshoot the problem. Another thing I would recommend it to loosen and retighten all the screws on the backside of the instrument cluster. Those screws hold down and also provides electricity for the various electrical components.
The main electrical wires for the UMCU that I would suspect would be the Brown/White, Red/Black, and Black wiring to the UMCU.
The P0500 code is probably a result of the problem stated above. If you think a sensor is causing the problem then try disconnecting it and see if all the meters drops out. We are talking about the sensor for the thermal transmitter, fuel level, VSS, and tach.
One last thing I'd like to include is that you can do a diagnostic test for the UMCU. It goes like this,
Meter Gauge and Odo/Trip Diagnostics
1. Turn the ignition key to ON (don't start the engine).
2. Change the odo/trip meter switch to "Trip A"
3. Turn the ignition key to OFF.
4. Push in and hold the odo/trip meter switch.
5. Turn the ignition key to ON (don't start the engine).
6. Release the odo/trip meter switch after one (1) second.
7. Push the odo/trip meter switch in and out three (3) times within five (5) seconds.
Note: All the digital LED segments should turn ON.
8. Push and hold in the odo/trip meter switch for about 15 seconds.
Note: ALL the meter gauges should start to move and hold steady around an imaginary horizontal centerline of the meters.
Good luck to all.