Ok first things first
I thought PHP Nuke came with a Gallery If not im sure theres a mod/hack to it. Check there site.
Secondly
version.php either doesnt exist or wasnt chmod 777
To do this. Find the file version.php right click in your FTP of course.
Look for permissions or chmod
Change the permissions to 777 this is so it can be written to and read from.
Also check what function is being used to access the file. check with your host or write a phpinfo file to see what functions are not allowed to be used. It may also be a reason.
Thirdly..
Ive never used the PHPNuke Portal.. but i think theres a folder called templates. If there is thats where templates go..
Otherwise go back to there site and read the FAQ. or post something in there forum.
Sorry if this isnt what you were after but i have never used PHPNuke and being honest i dont suggest newbies to use it unless they are going to learn from the syntax.