The importance of a good diet when you are trying to achieve a big goal is very important. It is not that uncommon for people to focus on the physical training for a run but then come race day not fuel appropriately and their race falls apart...
David will put you in the right direction and can help you set up the following:
Week to week healthy eating habits
Pre race carbohydrate loading plan
Race nutrition plan
Post race nutrition recovery plan
Being a Dietitian he often manages a lot of other underlying complex health conditions or eating related issues.