Since it was a demo, it's unlikely the shutter activation count is high. If it was refurbed for a different reason, it could have a high shutter count. My D4 currently has a count of 118,983.
For a $1,000 discount, it's likely a demo model is a great deal. If you're allowed to return it for full credit, all you would need to do would be take a single photo to know what the shutter count is. The D4 should last about 400,000 shutter actuations.