I looked up your plant online and found out that it is to be potted similar to the 'nuns orchid'. I also saw a picture of a healthy one and I'm thinking maybe you should show it to a local orchid nursery and see what they think. The roots look awfully suspicious and while spotting is normal on oncids I don't think the icky roots are a good sign at all. As I am definitely not a pro on this particular plant, I'd wait for a more senior member to chime in before you send it back. But in the meantime if you have some physan 20 i'd soak it and remove the rest of the spag. covering the roots. If there is black rot keep it a mile away from your other plants. Black rot can be awfully contagious. Wash your hands after you handle it, before you are around your other plants to avoid transferring any potential problems to your other plants.