update XBMC svn?

What is the process for updating XBMC 9.11 to svn r28256? Is it as simple as running XBMC svn r28256 from Launcher-Downloads? My current install is r26018, which was current when I installed XBMC from Launcher-Downloads back in January 2010.

I’d like to do this because all the extra skins from XBMC svn Installer are shown as incompatible. Will updating to r28256 solve this issue? Will my files (external USB HDD) be in jeopardy during or after update? Can the update be reversed? How? Thanks.

Yes, anytime you select one of the XBMC versions in the XBMC/Boxee → Downloads menu the selected version will be installed, replacing the currently installed version.