Replacing sending unit- how low does the tank need to be???

yeah ok...you want to bust your balls go right ahead....no thanks...not me....and if he wants to clean the tank? try doing that also with it installed...see how that works out for you

I don't know how you changed yours, but I'm 69 with some significant joint issues. I see no reason to drop the tank.

So far as fuel, I would EMPTY it. Siphon as much as you can, and then drain it using the supply tube fitting. Yeh. I'ts slow through that 5/16 fitting.