I moved a 500L system 3 times. First time, we lost some fish, second and third, lost nothing. First thing. This is a full days job. And you need two vehicles.
Put the return pump outlet in the first chamber, or use another smaller pump.
Take out 50% or more water before you disturb anything. I used 2*90L green plastic drums. The drums was on the trailer, filled by a pump and long new clean hosepipe.
Have 50% extra new fresh Salt water ready in other drums. If this can be dropped off at destination beforehand, it is better. Out of the way and less weight on the vehicle.
Fill cooler boxes with water from display. I used big Coleman coolers . Put Live Rock in cooler boxes. So that it will not tumble and move. Put small power head in each cooler box. And put your fish snails and hermits in the cooler boxes with the live rock. Balance the fish between multiple cooler boxes I had 3 boxes. Close the boxes. Fish will stress less in the darkness and they have more natural hiding areas. Put shrimps into separate small cooler boxes. One per box. I used the coffee cooler tubs. They are more fragile and might attach each other in a confined small place. Close that cooler container. Can open and close all the coolers every 10 minutes to let in fresh air.
Fill one extra cooler box with just water. This will be the first rinsing tank. Empty rest of the tank, Can rinse or move the sand a lot to get all the detritus buildup out while siphoning it down the drain. Make sure there are no lost snails, or peanut worms or anything else interesting in the sand. Depending on weight of sand in display, you can either leave it there or put it into another tub. Cover with just enough water to have it submerged. (5mm water above sand).
Drain the sump and DSB up to sand level. Move it out and get it on the trailer or bakkie. Refill it with water just taken up until full again. Put another small circulation pump in it to pump water from return chamber to skimmer chamber. Or use your return pump, that is if it is not too strong. Park the bakkie in the shade. So this vehicle have the 2 90* drums, new water drums and sump loaded.
Load the cabinet, and tank and if fitted wooden canopy, everything on second trailer or bakkie. Put all your electrical stuff, skimmer, other pumps, everything else inside the cabinet. Tie it down properly.
Now you are almost ready to go.
Put cooler boxes with livestock next to cabinet. Or where you still have space. And off you go.
Drive slow. Display tank on the front vehicle. And second vehicle keeping an eye out that nothing weird and wonderful happens. After 2km stop! recheck the rope work or tie down straps on the display. Sometimes stuff do move slightly and you have to tie it down again.
On the other side. Reversal. But first sent the wife to biy Pizza (lunch). And some extra beer.
First get cooler boxes with livestock inside the house or in shade. Re-connect circulation pumps, and keep lid closed.
Put cabinet in place, Display tank, but leave canopy and lights out of the way.
Empty sump again, but keep the water. Put sump in place, Refill, and put same pump back on again. Fill Display from the 2 90L drums.
Fill display tank with new fresh water. Get circulation with sump going.
Use that one extra cooler box. Take live rock out of live stock cooler box, and rinse it in the extra water, then put it into the display. Until all the rock is removed. Then take out the fish, snails and hermits and put them in the plastic bags, filled with water from cooler, and float them in the display. Now that empty livestock box, becomes the second rinsing box Should have about 50% water left in it. Take next live stock cooler box, and rinse the rock.
Let the bags float for 30 minutes. While you sort out all other equipment except the lights.
Release fish. You might have too much water in the system, so maybe do not release the water in the bags.
Put lights into place. Do not switch it on. Can test it, but leave it off. Put canopy in place. Dry the floor. Have a beer. Thank all your helpers / slaves. Have another beer.