I haven't tried htdig, but i use mnoGoSearch (
http://search.mnogo.ru/) on my personnal web site and it is very simple to install and configure.
The only problem is that you have to compile the sources, but once installed on an other distribution, you just have to tar the directory where all files are installed and to copy and untar this backup under SME.
If you want, i can send you the tar file with the binaries, documentation and configuration files.
Have a look on their documentation : many options are really interresting.