I was assuming you would show the reinstallation of the gauge onto the tank. I'm having trouble pushing it back on the tank. I'm afraid I will break the plastic tangs if I push too hard or tap it with a solid object..
It is difficult to get a good camera angle down there without the RV on a high lift. I had the same concern as you but I was able to do it more than once. Go slow and push gently but don't give up.
Could I also set it to empty if I know for a fact my tank is empty? I was using it with my camp stove and yes it ran out of fuel halfway through cooking my dinner lol.
The tank does not have to be empty to replace the sensor. But to calibrate the sensor you need to know how full it is. So I suggest calibrating right after you fill it so you know it is full and set it at 85% since it is never 100% full as it needs space to expand with temperature.