So what I'm trying to understand is you just want to update to the latest source build and retain your database? To update your source you just go to this link and download that latest compiled build.
http://code.google.com/p/projecteqemu/downloads/list
Now if you want to compile to the absolute latest build yourself, a list of all the changes and builds can be found here:
http://code.google.com/p/projecteqemu/updates/list
Now you don't have to change your database in anyway, but you may get errors because new tables have been added and stuff. All you have to do is source these particular updates in, which isn't hard. You just find out when the last time you updated and then add in all the svn updates up until the latest. These don't overwrite anything you have worked on. All of these updates can be found here:
http://code.google.com/p/projecteqem.../utils/sql/svn
Hope this helps.