At a glance, I believe TBC Cosmo's find invocation should do the trick for you. Like anything, you'll want to test it before running it on a production system.
As a related aside, I'd recommend that you read through a brief guide I wrote up some time ago on removing/disabling old users.
It was written for FreeBSD originally, but the same commands should apply for Linux (except for chpass
-- you'll need to use chage
instead). There are some post-user departure steps that should be taken as a matter of policy. And you might even consider disabling (as opposed to deleting) users to keep something of an audit trail around.