yes, so the thread is for the M156 (ME9.7 Computer). Your engine is the M157 which has the (MED17.7.3 Computer).
best if you create a separate thread with your question. I do have to say...response from HPTuners in the Mercedes forum is pretty much non-existent. same with submitting a technical support ticket unless there is something broken in the software.
again, from what I know, HPTuners will pull whatever exists on the computer into your base map. I cannot speak in regards to if you have a previous tune if it will download or present error.
http://www.hptuners.com/help/