Alternatively you can use a system like xampp. That's a package of apache, php, MySQL and many more to run systems like XOOPS on your workstation/server. Download @http://www.apachefriends.org
When you want to update your Site from 2.0 to 2.2 you have update to 2.0.13.1 and then update to 2.2.2 and then to 2.2.3RC1 You find the necessary files @ "Download Xoops"
login to your admin page (www.yoursite.com/admin.php). Then go to System -> Groups. There are after Installation 3 groups: Admininstrator/Webmaster Registered User Anonymous User
xoopsgallery only works if your server has NEtPBM or imageMagick installed. This has nothing to do with the module. It must be seperately being installed by yourown. If you have no access to your PHP installation, you have to ask your ISP to install it.
the user created during installation has Admin rights. But you can give any user Admin rights by putting desired user into Admin-Group(located at System->Groups)