Upgrading OS questions

I need to upgrade my MacBook Pro's OS from 10.5.8 to be able to sync with my iPhone. My questions are:

1) How far up do I need to go? I do have the CD for Snow Leopard, will this be enough to get the most recent update of iTunes? (haven't installed Snow Leopard yet)

2) I'm using Microsoft Office 2008 (Word only) 12.1.0 and have read that it must be updated also. Can I update straight from 12.1.0 to the most recent 2008 update, which appears to be 12.3.6?

I guess those are my main questions. All I really need/want to do is to be able to sync my iPhone again. I would appreciate any comments, suggestions, advice on this. Thanks!