As an ex-AVAYA Engineer I can tell that S8300 is a good product. Based on what you ordered you will need some training to configure and use them expertly.
On a user level it is almost plug and play!
I would suggest playing with them in the lab and first opening the Quick start guides before reading the user's guide which is long.
The Quick start Guides are short and right to the point,quite straightforward and give you a feeling of the things very quickly.
For the network manager it means learning more on VOIP, Definity(Not as much as you needed for Definity itself) in addition to data switches.
Most probably you bought some kind of GUI based management also.
For the network manager and advanced technician with proper authorization, knowing the CLI, some Linux might be handy.