Voltmeter issue is normal. The glowplugs and intake heater pull a lot of juice initially, and it shows on the gauge. As long as the gauge comes back up to 13-14v after a short bit, you're ok.
Fuel gauge issue could be the sender in the tank, too. The little rheostat can get a dead spot in it, usually from 1/2 tank down. Same thing happens with my wife's Blazer. I have to replace the sender one of these days.
Speedo getting "stuck". Can you give more info? Does it stay in one place for a while, then come back down to 0 at a stop and/or start working normally again? If so, then thats probably the stepper motor.
01-02 usually dont have issues with the steppers, so check everything else you can.