Is a discogram procedure extremely painful?

Yes. But this test is usually necessary to determine if your level of disc abnormality on the MRI is really an problem or not. Many times the bad disc is not visualized on a MRI done while lying down. The discogram injects saline into the disc creating pressue in the disc simulating gravity effect whil standing, if the disc is bad the disc wil extrude and cause pain but you will know you need surgery.
No. Discography is typically done with conscious sedation. Although the goal is to replicate your pain, analgesic confirmation (infusion of local anesthetic into the disc), aka fad (functional anesthetic discography) is becoming more and more the norm.