Changing tourist L to a X2 visa

Hi, I am wondering if I can change my tourist L to the X2. I will be studying in Beijing in July and I have entered the country in early June with a tourist L before my university can provide me with the documents. I heard that I can go to the local exit and entry bureau in Beijing to do the conversion. Can someone let me know if this is actually possible? If this is possible, what documents do I need to bring and how long does the process take? Thanks a lot!