I have rearranged my scape a number of times. Take out as much water are you need to put into a tub and cover your rock and coral with. then you can start to replace the rocks the way you want them. Replace some of the water and put some new saltwater in like doing a water change pretty much. Does not take long as our tanks are pretty small. Try not to mix the sand up at all.
FWIW I like the scape you have. Nice open area in the middle, a good arch.