Via Napoli is on the Dining Plan as a "1 TS" location.
For entrees, 1 credit will get you either 1 of the "normal" entrees (non-pizza) or 1 individual pizza. For larger size pizzas, the 20in costs 2 credits and the 1/2 meter costs 4. It's unclear if (but I'm assuming that) only adult credits may be used for the 20in and 1/2m pies.