Linda, you have a few options. You can train for the Half with the Byrd Park Group (free). There will be a spring marathon training group that runs out of Byrd Park also (free ~$10) and there is a Galloway program ($95) http://www.active.com/running-membership/richmond-va/richmond-va-ga.... There usually is a group that carries over from training for the Richmond Half/full marathon that runs Shamrock. They usually post something on this message board.
Another great option is to train with Team in Training, which has programs for both Shamrock's full and half marathon, as well as other races. With this option, you get the satisfaction of knowing that you are helping find a cure for blood cancers. www.teamintraining.org