You do not run the install from the main pp directory as the documentation states.
You would not run install.php when doing an install
You might also want to read the complete upgrade instructions under the documentations folder of the downloaded code as most issues upgrading have come from not reading the documentation when upgrading to PP8 from earlier versions and using vb4.
For example I do not know what you mean by it doesn't look right but I could guess if your integrating with vb4 you definately probally have not installed the plugins. There is a whole section dedicated to that specific forum style. Your gallery will not look correct until such time as you generate and install the xml file for vb4.