I disagree, here is what I would do. My method would create a pristine tank condition and give every thing a greater chance to survive.

First off, how many of these corals are encrusted, the less the better, but you can chisel even encrusted corals off of their rock. Secondly, LPS are hardy little suckers, and are very difficult to kill. They can tolerate quite a range of swings without dying. The SPS on the other hand are delicate creatures and will have to be transferred accordingly.

Again, I would remove every coral you wish to save and place them into the tank supported by a pvc and eggcrate structure. I would then follow Sean T's method on reefcentral.com for "cooking" liverock and cycle the rock this way. It will expell any waste the rock has collected over the years and allow your system to become trully barebottom instead of phosphate enriched rock with no sand.