If you're asking such a question, you'd better to hire somebody to to do it for you. As nobody here knows what you've got there in your copy of exim.conf. Is it anyhow customized? Or is it a default one? So feel free to PM me if you need my help, or look at advertising forum here for other guys.
Presuming, you've got default exim.conf 2.1.1 then it's quite safe to update to SpamBlocker4. Make sure to read release notes and remarks before you install a new version on your server. Make sure also to backup the existing version of exim.conf and exim.pl.