Replacing wet soil is not the answer because it often does more harm than good. That being said, here is what I would suggest you do now.
Carefully unpot the plant and remove any loose soil, not in direct contact with the roots being careful not to damage the tiny root hairs. Cut away any roots that are dead, soft or mushy. Move the remaining rootball into the SMALLEST pot that it will fit into snugly. Use a peat-based potting mix that has added perlite mixed throughout.
The purpose of the small pot and porous potting mix is that if the roots are to recover, they will need regular infusions of oxygen around them. Large pots and heavy soils prevent that from happening.
When you water, add just enough so that the top inch of soil feels dry again in about 1 week. You will have to experiment a bit to get the right amount.
