For a public service site like that I’d suggest looking into “top tasks” - http://alistapart.com/article/what-really-matters-focusing-on-top-tasks is worth a read, or do a web search for “gerry mcgovern top tasks” for more on the subject.
As you’re doing this revamp, and along with “top tasks”, it’s a great opportunity to remove old, stale and little used content so you can concentrate on what your customers actually want.