Many performance metrics for NetApps are not exposed via SNMP (e.g. read/write latency per volume.)
These can only be accessed via the API.
Some free tools, with the right amount of cajoling and tender care, can get these.
A commercial solution such as http://www.LogicMonitor.com/ will automate the entire configuration, collection, graphing and has best practices alerts pre-defined.
Depends on whether you have an excess of time, or are willing to trade a little money for a lot of freed up time.