Remove as much as you can. Take out your fish and put them in a bucket with the water. If your rocks are stacked, unstack them so that they are lying flat on the base of the tank. You don't want anything falling and breaking the glass. Drain the water down as much as you can to make it lighter, leave in the rocks (if they're not too heavy, or else put them in buckets also).
It's not really that difficult, just time consuming. You'll spend a good part of a day doing it. Taking your fish out and putting them in a bucket will stress them less. If you leave them in the tank, the sloshing water will stir up debris and get in their gills and cut them.
You want to have...--->:happyfish