My '08 Santa Fe with only 63K miles took a notion after my last fill up to not register a full tank on my fuel gauge. In fact, it registered nearly empty and soon the low fuel light came on. Several days later, I decided to fill it up again and it only took about a gallon and a half. The fuel guage did, however, move to a quarter of a tank even though I know the tank is completely full. The fuel needle does move at start up--just not to the full indication. Also, the fuel "range" indicator shows zero. Is my sending unit at fault or is it something else? Hopefully, it is something I can repair myself as I do not have deep pockets. Can anyone help? What part number might I need for repairs?