Gas gauge not working, replace sending unit or gauge first?

[slam59]

My gas gauge on my 74 C10 is not working right, left me without gas over the weekend. Is it usually the sending unit that goes out more often than the gas gauge itself? I was wondering which should be replaced first? Is there a way to trouble shoot and tell which one is bad? My friend thats my mechanic on my ride says that the bed has to be removed to get to the tank to be able to remove the tank and get to the sending unit, says there are metal bands in between tank and bed that are in the way. Is this the only way to get to the tank?