I don't know about Space X, but 3D printing tech was used the first time in 2013 year, for printing some of the pumps used in the engine.
So, it's safe to assume, that such an innovative company as Space X could be using this technology for several parts of their rocket and engine.
Also, good luck and congrads to Space X team and Mr. Musk. This is a great step forward. Another leap for mankind!