Bad voltage limiter? (New owner!)

First off, welcome aboard. Wouldn't worry about the temp gauge. Bottom of the normal range is where a good Mopar wants to run. At least that's where most of mine wanted to be. To find out if you need a new sending unit get under the car, disconnect the wire going to the sending unit and short it to ground. If the gauge doesn't read full when you do this you have a bad gauge or the ground strap on the fuel line is open. If the gauge does read full you have a bad sending unit. If a shop told me it would cost $1000 to change it I would find another shop. You don't even need to drop the tank to change the sending unit. You want to do this with the tank nearly empty though. Ran mine out of gas, put in 2 gallons and drove it home and tore into it. Run the car up on a lift and the rear end will sag far enough to allow you to remove the tank ring and the sending unit and put in a new one. I changed mine in less than an hour working off jackstands and the ground. If you do this yourself, don't forget to lubricate the the rubber ring that goes between the tank and the sending unit or it will leak when you are done. Hope this helps.