Great Real Estate provides functionality to turn your WordPress installation into a content managed real estate website.
The plugin author has set up a Forum for support questions and announcements at http://www.rogertheriault.com/forums/
Please don't email the plugin author directly for support, please use the forums - so that other users can also benefit from the questions and answers.
generally, they are the functions in the PHP file templatefunctions.php. But please visit the plugin homepage for complete details on all the tags, and how you can use them in The WordPress Loop.
Simply create a localization file for your language and/or locale. You can use the existing translation files as a staring point.
Probably. See the website tutorial on customizing templates. Avoid changing the core code.