Is your old version of SVN also built from source, or is it installed from a RPM ? If the latter, I would remove the old version using "zypper remove" or "rpm -e" before you install the new version.
Building SVN from source is pretty straightforward - these are the commands I ran on SuSE 10.2:
tar zxvf subversion-1.6.6.tar.gz
tar zxvf subversion-deps-1.6.6.tar.gz # Puts dependent files in subversion-1.6.6 tree
./configure --with-ssl # Use with-ssl if you want to access your SVN repo via https
sudo make install # Installs to /usr/local/bin by default - use the --prefix option for configure script to change the install location