It was <i>svn swich</i> i was thinking of. You should do <i>svn switch .... .... >log.txt</i> and then examine the logfile afterwards to see that you didn't have any conflicts. (Marked with C in the beginning of the line).
There are also some database changes, so i suggest you read this document: http://ez.no/ez_publish/download/changelogs/ez_publish_3_5/upgrading
And ofcourse you make a backup before you attemt this switch.