A good place to start is at Deutsche Dienststelle - http://www.dd-wast.de
- where they keep records of german soldiers or volunteers. They charge a bit to conduct a search, but it is money well spent in the cases I know of
I also have a bit of experience with Bundesarchiv in Berlin, who also charges a bit but where I have found good information about a volunteer I was searching for.
So that should get you started
Not a lot of info on the unit itself - I don't know of any "black units" under Nordland, but perhaps someone else knows about this