Here's some pictures. The soil in my hand is the soil it came in, not that wet though

Just-delivered plants are always stressed and transport and storage damage is really common. Photos would probably help!

Unfortunately, if it was delivered during a blizzard, then cold damage (or at least cold shock) is also possible if it wasn't well-insulated and temperatures fell under about 45 in the package. They really don't care for chillier weather or temperatures, or even drafts of that temperature or below.

If roots were squishy and black, it's OK to remove them back to the healthy roots. That's also a shock but squishy and black areas are not healthy and replacement when repotting anyway is completely fine. Replacing with fresh, light soil is also good.

Peace lilies don't like being overwatered (they're tolerant of a lot, but contrary to opinion, would rather not sit in water) and do prefer a light mix.

As this sounds like a recent order, I'd contact the company and see what they can do for you.

I wouldn't at this particular instant, but if damage continues and you see continuing signs of root rot as well, you can combat it with 1 part hydrogen peroxide (3% from the drug store) and 3 parts water. It helps to disinfect the plant. It's not perfect, but does help.

Thanks! Also, I have pictures in the