Practice casting in the yard for extended periods before going out and fishing for a long time. Elbow and shoulder injuries are common if you are under trained.
I think its better for people to come from traditional surfcasting backgrounds then to fly fishing. I think a lot of people who came to fly fishing first migrated over to surfcasting because of the difficulty involved in finding fish within 100 feet. Your experience makes you a perfect canidate to take the sport.
You're in the right place. Cliff fishing with the fly rod is very effective.
My favorite fly is the White Water Witch - which was developed by an Aquidneck Island fly fisherman for cliff fishing. This one is tied too long for my liking - but it's easy tie. The black presents a contrasty silhouette in the white water.