my plan was to temporarily remove the livestock, water, rocks, etc. and move the tank. Then put everything back in the original tank and wait for the arrival and cycle of the new one.
What happened of course was that the old tank burst, the livestock got evacuated into tubs and small QT tanks for a couple of days and I had to think about what to do now.
I chose to buy a temporary tank (75 gallon) and keep the livestock in there.
Here's the important part: I DID NOT move the sand. My temp tank is bare bottom since I did not think the little temp tank could handle the release of nutrients/waste from a disturbed sandbed.
The 75g is holding all of the original liverock (some of it is in the sump) and things have actually gone really well in there.
I did sell some livestock: an oyster because I can't commit to phyto dosing right now and I'd hate to starve it, fighting conchs because I have no sandbed, some clams and corals because my future tank is going into a different direction, etc.
But the fish I love are still here and are doing really well in the 75g.
I was in a rush to get them out of the tiny 10g QT and probably paid more for the set up than I will be able to ask for it in a couple of months but it was well worth it to safe my critters.
So if it was me, I'd look at what you want to keep, what you don't want to keep, what wouldn't do so well in the temp tank and go from there. If you move the liverock but not the sand you might be surprised how easy it is.
Good luck in whatever you decide to do.