OK... On '98 & '99 it's like this:
The fuel gauge sender has 3 wires. One is ground, one goes to the gauge. The lt.green/red wire goes to the low-fuel warning light. When the gas is low the sender connects that wire to ground.

So you wanna find that wire, check it back at the sender. If you unplug the sender, & the light goes out, the sender is bad. If you unplug it & the light stays on, that wire is shorted to ground. Get a DMM & start looking for someplace between the sender & the gauge, where that wire is touching ground. Fix the insulation, tape it up, or something like that.

I don't suppose they changed much to 2000, but I'm not sure. If they didn't change anything, then my Helm book would have said '98 '99 AND 2000.