Given the fact you damaged the cover glass you may want to get your camera to an authorized Nikon repair center or ship it to them for them to replace.
Opening the camera to the point of even getting to the cover glass is a lot of work! I strongly recommend you review the Nikon D600 Teardown This is not a good first time project to attempt.
Even once you get to the sensor Step 23 to replace the cover glass you can easily get dust in between the cover and/or filters. You really need proper equipment to do this right to control the air flow and dust protection (clean room).