I had my dogs x-rayed when they were under for their spay/neuter surgeries, but sedation is not a requirement. There are check boxes on the OFA form about whether or not sedation was used, and what type. I did prelims rather than wait until 2 years to get a rating since a rating didn't matter to me. I just wanted to make sure hips and elbows were healthy, especially with Halo since I planned on doing a sport with her.
The x-rays will cost more than the OFA fee, which was only around $30 if I remember correctly. I had my regular vet do the x-rays. Prices will vary depending on where you live.