[otrs] OTRS upgrade from 2.1.4 to latest stable

Hi, I have OTRS running nicely on a centos 4.4 box and I would like to upgrade to the latest (preferably using rpm) but I can't find upgrade documentation anyware. Can anyone prove me with tips or hints? 2.1.4 is from an rpm so am I likely to have any issues with this? Many Thanks, Josh.