Dropping the gas tank is not difficult, it can be done in ten minutes. And you don't have to replace the fuel pump to replace the check valve. The check valve is inside the fuel pressure regulator located on top of the fuel pump.
I would MUCH rather replace that than cut the fuel line, insert a check valve, and then hope it doesn't leak afterwards.
Here's a pic of the fuel pressure regulator taken when I replaced mine a few months ago. It is held onto the top of the fuel pump by that snap-in flat spring steel clamp you see on top of the old pressure regulator.