I ordered the voltage reducer from chevyduty that was said to go, "inline" I assumed that meant inline between the sender in the tank and the gauge. It conected to the sender wire fine. Shound I have installed this reducer, resister, on the hot lead that is now 12 V or was I correct in putting it in the sender line that connects to the tank?

If you need a tool and don't buy it, you will find you have paid for it and don't have it.