I have had a similar problem with heavy pots. I usually put down an old tarp and gently roll the pot over on it. Using an old kitchen knife or machete run it around the edge to loosen the soil and roots. Using a curved tool or your hands grab the dirt and work it to pull the plant loose and out. Add a potting soil and about add about 1/3 of its volume with perlite. Put the soil in the bottom of the pot so when the plant is put back it will be at the correct height. Add a small amount of the proper fertilized and a root stimulator.
