Is there documentation for installing onto my shared linux server?
There sure was! I don't know where it's gone. I can't find it either. I'll raise a sourceforge.net help ticket and find out where they have been moved to or if they still exist.
As for installation on a linux host, if you are using an RPM distribution then install the RPM. Else untar the tarball and move the htdocs/ directory to /groogle in the root of your /var/www/html/ directory (or equivilent), the /log and /upload directory to /log and /upload in the web root respectively (these locations can be configured later for better security).
From a command shell run the patchdb.sh script from the /db directory found in the root of the tarball. This will install the database schema.
Once you've done that you can point a web browser at your web server and browse to http://server/groogle/ which will tell you if you are missing any php libraries.
Under the htdocs/conf/ directory there are a set of php configuration files. Most of the settings are fairly self explanatory/commented.
If you have any more questions or installation problems then post them here and I'll do my best to help you out.