You'll find the manual definition update files (as well for client as for the AV server) on this page:
http://www.symantec.com/business/security_response/definitions/download/detail.jsp?gid=savce
Migrating to SAV10 will not be possible, you'll have to go to SEP 11. Whether it is time consuming, it depends on how big your environment is. The upgrade to SEP11 goes automatically as of SAV9 (uninstall SAV and install of SEP).
Dries