Todd,
I am not familiar with Python, so I don't know how to access DLLs in this environment, but documentation for the Traditional NI-DAQ functions is available in the Traditional NI-DAQ Function Reference Help. This is available in the following location:
Start >> Programs >> National Instruments >> NI-DAQ
With regards to the NI-DAQ source code, this is not publicly available. However, the documentation should provide you with the information you need to use the functions.
Good luck with your application.
Spencer S.