This is a pretty good reddit post attempting to give you a Russian perspective: http://www.reddit.com/r/worldnews/c...its_armed_forces_on_full_combat_alert/cfs2gz4
Also, why wouldn't they need Sevastopol? It's the primary base for the Black Sea fleet.
They don't need it because they are moving the fleet to Novorossiysk anyway. They decided to place all future units there because they got tired of Ukraine constantly meddling with how they ran Sevastopol. Back when Yanukovich stated that he wouldn't renew the agreement beyond 2017, before he flip-flopped, Russia didn't do a damn thing.
That post is somewhat biased too. Deploying troops to protect the Crimean opposition, really? Kyiv didn't do a damn thing to the Crimean opposition. The post is also either outdated or lying because surrounding Ukrainian military positions in Crimea and basically daring them to do something about it sure as hell wasn't part of any agreement.