samba - Sep 1998 - Older version, upgrading, performance...

Hello All,
     
     We are currently running the 1.9.15p8 version of Samba.  It was 
     installed by someone else, and I have had very little experience with 
     the software, other than making slight modifications to the smb.conf 
     file.  Our current version works, but we take a pretty big processor 
     hit on our server (20% CPU usage) whenever we read or write from a 
     Samba client running NT.  Also, the read and write speed is 
     significantly slower than non-Samba clients.  How easy is it to 
     upgrade, and what is involved?  Will I see better performance with the 
     newer version?
     
     Thanks,
     
     Sean McGuire