Tank Move Questions

[moppy]

Moving my tank from 2x 40 gallons upstairs to a 120 gallon.

Just curious about sand??? I bought lots of new "LIVE" sand but was told I should seed it with my old sand. True?? If so how much of the old stuff?

Also, should I take as much water from the old tank as I can? I am assuming I should...

Any other thoughts on how to make this relatively painless on my existing fish and corals???

Thanks