Do I have to be an experienced hunter/fisherman/shooter in order to participate in FCS events?

No.  We have all types of sportsmen at FCS events, from novices to veterans.  We delight in teaching others what we know.  However, some events require a certain amount of familiarity with techniques in order to be successful.  For example, it would be better for someone who has never shot to learn how to hit clay targets before trying his hand at dove hunting.  It would also be better for a novice fisherman to learn how to plastic worm fish before signing up for a guided bay fishing trip where the bait will be croakers and/or piggy perch (which have a bite similar to a bass hitting a plastic worm).