Does it make a difference in energy if a reaction is done in many steps or in one step?
You might want to take a look at Hess's law. It states that the total enthalpy change during the complete course of a reaction is the same whether the reaction is made in one step or in several steps. But that covers only the thermodynamic aspect. In reality, you also have kinetic barriers (activation energy) which add to the energy needed for a reaction to run (or released during a reaction). That's why catalysts are so useful: They break a reaction down into steps (involving different intermediates) with lower activation barriers than the original reaction so that the reaction as a whole can proceed at a lower temperature.