You might consider a very gradual switchover so that your body has plenty of time to adapt so that you will minimize the strain and tiredness that might accompany a violent change in food intake. Remember that your entire body including gut microbes is adapted to your current diet so it can be a bit of a shock to suddenly change everything. The downside of slow change is it can drag out carb cravings for some people but I have seen others who do not seem to have to deal with much in the way of cravings at all. To bad there is no way to know in advance how each individual will respond. o
Of course, the best things to start cutting out of the diet are items with low level of nutrients like most grains, flour, and sugar. Replace them with nutrient dense healthy foods and fats. If you have a heavy workout schedule, you may do better with more carbs than the average paleo dieter, but again remember, mileage will vary from one individual to another.
Also keep in mind that the kind of training needed to become a professional athlete may will be an amount of exercise that is inherently unnatural and hard on the system to start with. Conservation of energy is the natural state of most creatures. SOme exercise is natural, but you will not see many creatures naturally working out far beyond what is needed to obtain food and mates and rear young, and for some animals, perhaps a bit of horse play from time to time. The elite athlete is basically attempting to push him/herself far beyond what is natural and normal and thus you will probably have special needs beyond the regular population.