i know it sounds contradictory, but the easiest thing would be to remove your fish rock and coral to a separate holding container(s) ...think rubbermaid totes or 5 gallon buckets..., drain most of the water out and save it (or at least half), remove the
crushed coral, rinse your new sand (unless you bought live sand from your lfs, in which case you just add it directly with no rinsing), then scoop it into the tank (keep in mind the tank is empty at this point). then add back 50% of your water (you might have this pre-mixed and kind of look at it like a 50% water change. just be sure its chemistry is very similar to your current water in the way of ph, salinity, etc). then add back your LR, then your corals, then your fish.
im sure the live rock in a 4 yr old tank wouldnt hurt from a good dunk and swish treatment while youre at it.
