Has there been a recall on a 2004 trailblazer gas tank

There is no recall for any fuel tank issues, You can read the lists here. 2003 Chevrolet Trailblazer Recalls RepairPal

undo all the fuel lines and vacuum lines, electrical connectors to the fuel tank. undo the fuel filler tube at the tank. support the gas tank as it will be heavy depending on how gas is in it. undo the fuel tank straps and lower the tank. clean the area around the sending unit of dirt and remove the lock ring that holds the sending unit into the tank then you can remove the sending unit to replace the pump. follow the instructions that came with the new pump. don`t use a used pump and change the fuel filter.

Under the drivers side in front of gas tank

This sounds like the fuel level sensor in the gas tank is going bad, or there is a bad ground at the tank. A technician using a scan tool can monitor the actual fuel level data to verify.
Another possibility is a bad stepper motor in the instrument panel, each gauge had a stepper motor to drive the needle.

Vent soleniod located on gas tank filler neck is faulty

Just fill the gas tank

Replace tank level sending unit.

THIS PROBLEM IS CAUSED BY A DEFECTIVE GAS GUAGE SENDING UNIT, U WILL NEED TO PULL THE FUEL TANK AND REPLACE IT.

If you mean that the gas gauge is floating and you do not know the amount of gas in the tank, then the most common cause for this is the fuel level sensor in the tank. The fule tank would need to be removed to replace it.- Tech jk