Honestly I think you have a lot more on your hands then you think. You basically are prepping for a move.
You will require lots of totes, lots of heaters and lots of pumps. You also risk chemical ammonia spikes. Basically set up all the totes, heaters, extension cords and pumps so they are ready. Drain the tank into the totes evenly and as you get down to rockwork move pieces into the totes. Get the fish out before the water level gets too low. Also do not remove the base rocks as that will stir up a lot of crap poisoning the water. Keep draining the tank until you no longer have clean water to drain out. At that point remove the base rocks. You may want to have a lot of NSW on hand to top off the totes. You will be left with the substrate and murky stinky water. I personally recommend removing the sand and getting new at that point. You can rinse and reuse the old, but it is a lot of work to clean the sand for what it is worth. Using as is will most likely nuke your tank.
Then onto fixing the tank.
I would also reevaluate the tank design so that if anything happens in the future you are not stuck in the same situation. Tearing the tank down should be the absolute last thing you try as it is the riskiest.
Maybe before you risk it, post more details and maybe someone can come up with an idea you missed.