Well... this is not an easy step, all the time.
Disturbing the substrate may cause problems.
There are a few MOVE threads on here.
Using the rubbermaid 100 will be good. Move the LR and the water straight to it. Leave the substrate. You do not have time to let it settle and rebuild the diversity.
Set the rubber maid up near where you are putting the new tank. Just not in the way of building.
This will keep your motivation moving forward as you do each part.
You will need to cycle this new tank anyway. So seeding it with some of the existing rock will be a breeze.
Check where you are putting the new tank, make sure the floor can support it and your electric is good, as you will have a FEW more things plugged in than before.