None of the documents available for download go into specifics about the operation/description of the controls, indicators, or connections. I've downloaded documents for the FAS20xx and for the DS14MK2, but none of these are useful in this area.
Is there a service manual or other type of user manual that would tell an 'all-thumbs' person (like myself) the purpose/function, etc. on these units?
Indocators are described in Platform Monitoring Guide (https://library.netapp.com/ecm/ecm_download_file/ECMP1112529). Not sure what you mean under "controls" but usually there is none - it starts on power on without any manual intervention. Connections are outlined in System Installation and Setup - you should have it if you downloaded the whole documents set for FAS2040. All of them do assume that you are familiar with basic concepts (controller, shelf etc).
I think you would get better responses if you asked more precise questions. Are you NetApp partner by any chance or do you have some training units for NetApp University? Web based trainings for platforms are good and provide exactly what you ask, at least those that deal with servicing them.