SFDC sync and data cleaning

Hi, I'm a new user to Marketo and have a 2 part question - 1). we've been told in our discovery sessions that we need to sync all records between Marketo and SFDC - our instance of SFDC is a complete mess, and ths would be a disaster! Is there a way of syncing leads/oppties so we get to see when a lead status changes or it converts without the full sync? 2). My Boss is adamant that data can be cleaned from within Marketo or by a simple plug-in tool - Ringlead, Reachforce...which has proved the best for any of you?