I want to be a bone marrow donor. How painful and risky is it?

A potential bone marrow/stem cell donor swabs four areas of their cheeks and places the cotton swabs in a package.

http://www.theglobeandmail.com/life/health-and-fitness/ask-a-health-expert/i-want-to-be-a-bone-marrow-donor-how-painful-and-risky-is-it/article13939249/?cmpid=rss1