Dear Mr. Brown,
Since it is a cloud based solution you really do not need to have technical knowlege of most of the mentioned technologies.
If you want to extend the solution using PDI solutions, then you need technical knowledge of ABSL & SDK.
If you are integrating C4C with CRM/ERP then you need technical knowledge of HCI/PI.
For UI you have to learn how to adapt it (its more configuration not technical).
Most of the other things including Application/ABAP code/UI/Framewok/DB are maintained by SAP.
Regards,
Suman