Welcome, dhunsaker. Schefflera arboricola so not do well with very wet roots. You need to allow the soil to dry from half an inch to a full inch. In the winter months, when growth slows, it is easy to over water. The nice thing about these is that they are tough plants and yours should recover. They need bright light but not directly in a window. If your indoor air is dry due to heating your home then occasional misting may help.
If you have blackening branches, go ahead and trim those off. Even if it loses all or most its leaves, you should see new baby ones soon if it is in a happy place.