I am curious about this also, for my 2008 Chevy 210P. Possibly no one answered because it might not be a viable way of changing the pump. I have read that some early models have a door or hatch in the floor for this purpose, but I have not been able to get any details.
Cutting a hole might be more effort and/or involve more problems than dropping the tank.
I would hope that someone with experience doing the change out could comment.