What kind of documentation are you looking for? It still runs the same Data ONTAP 7G, and these manuals are still available. Hardware overview including on-board ports layout is still in HWU. And knowledge base still contains articles about old platforms as well.
Unless you start completely from scratch and has never touched any FAS before, I’d say available information is pretty good to work with it.
So may be you need to elaborate on your question - what information do you need?