"also, the idle is acting a little funky. when i start it, it jumps to about 1900 then settles to about 700-800 (tune is set to 700). after a little bit, though, it'll slowly drop to around 500 & occasionally dip to 475-450-ish when it's in neutral or with the clutch in."

By your year i'm assuming you have a throttle cable style intake and not fly by wire. I am not sure but it may be your throttle positioning sensor or motor. These two items are located on the drivers side of the throttle body and could contribute to your wierd idle because in the winter when its cold my v6 does the same thing and my mechanic told me it was one of these culprits. As far as your guages and tach not working i don't have a guess on that one...