Either through that or phpBB restore feature. In all honest, I suggest you take a second backup of the database you are moving via phpMyadmin, just to be safe, phpBB's backup feature can be a little iffy sometimes.
You need to set the permissions in Forum Permissons first, and make the forums private that you want the Group to be able to work with, and then you can set specifc things for the group in the group permissions panel.
Check the MOD DB and MOD release and annoucment forum for this modifciation. It is something you have to install seprately for phpbb. Try Searching for "quick reply" and it should help you find what you need.
You willl need to check in all the .tpl files that modification edited, but you will need to either use the Topic for this mod in the MOD release and anouncement forum, or contact the author for support
As far as I can tell, the template by defualt doesnt have a private message link at the top. You may want to ask at the theme authors forums or in our phpBB Styles Development and Discussion forum, and see if anyone could help you create a Button t o add a direct link