The ground buss on a 2000+ looks like a rectangular connector with a few black wires going into it and one tab on the top bolted to the body of the car. Typically these don't seem to be giving folks issues.
The fuel gauge and oil pressure sender are two items that are common. The OP sender, I'd suggest changing and the level sender on the tank is odd. Try checking the square connector on top of the tank at the sender. That is the one that controls level. The oval one is for the fuel pump.