3 days ago gas hand starting jumping form full to empty after I filled up. today I turn the corner truck shuts off. wont start. Thought it was out of gas Put gas in. Still would not turn over. Called tow truck got truck towed to repair shop. Once he dropped the truck it started right up. I was told I need a fuel assembly at $600. Any suggestion?? Help!

From your description of the problem, I would suggest you check and make sure the ground to your fuel tank and fuel assembly is clean and tight, and no wires are broken. It sounds like you have a bad (loose) ground, which would cause both the fuel gauge to jump around, and the fuel pump to quit unexpectedly, like on a hard corner. Dropping the truck could jiggle the loose connection so that it worked, again. Before spending the $600, make sure your ground is good. If the bad ground is inside the unit, then you will have to get it replaced, but make sure it's not just a loose wire, first.