You need to specify the amperage requirement and operating temperature to answer this.
no it will only decrease the current carrying capability
You'll need RCA style cables to connect from your headunit to the amp. You'll then need Speaker Wire to run from the outputs of the Amp to the speaker terminals. You'll also need a heavy gauge power wire. A wiring kit such as the StreetWires Power Station PSK04Ri 4-gauge amplifier wiring kit.
You first need to discover what is wrong. It can be the gauge, the sending unit (the part that measures the gas in the tank), or some associated wiring.
need to know where to tie in to the fuel gage have a black and white omming out of fank
at least 4ga wire but it would be best to get 4awg or 0awg. 4 gauge is smaller than 4 American gauge wire
The gauge, wiring or sending unit is bad.
Failed gauge, wiring, or level sensor.
it will be printed on the wire
Bad gauge, bad sending unit, bad wiring.
There could be a few problems....wiring issue, the gauge in the dash has gone bad, or the sensor for the fuel float is bad, id check wiring and the gauge first because sending units are expensive and can be a pain to change
Check the float by pining the wiring at the tank the gauge will go to full if not the wiring or gauge may be defective
Connect the wiring harness to the back of your oil pressure gauge. Secure the oil pressure gauge with the retaining screws.