The prices must have gone up, or they are quoting you the original unit. The upgrade in tank sending unit was $250 - $300.
To answer your question, Yes, the Fass and Vulcan will solve the problem. The only thing you will have to do is secure the leaks on top of the tank so water and debris does not get in.
If you have not done any performance upgrades to your truck, I'd go with the in tank pump sending unit, and keep the carter block pump.