Why don't you check with your employer? I am sure they always looking for employees to be a certified first aider (it is required by law that there is at least one certified first aider available at work at anytime). Your employer will pay for your time and the course.
CCC, don't worry about getting into trouble by helping people. A certified first aider (by St. John, cause I am) you are insured by St. John as long as your certificate is valid. So far no certified first aider has been successfully sued by anyone under St. John.
In fact in some states in the US, if you don't offer help to people who indeed needs help you might go to jail because of their Good Samaritan law.