Your latest issue has been answered several times already in the forums. Just search for it and I'm sure you'd find it. My immediate suggestion, without having to search the forums myself, is to copy config.new.php to config.php. Edit the values in config.php and upload it using FTP.
Database server host is the name of the host, or box, where the database server is running. For most installations this is just "localhost". Give it a try.
I didn't understand you last question too well. I can only say that I looked hard for a database/script driven image gallery solution and there is NOTHING out there that does a better job or has more features than 4images for its price. Great value in my opinion.