I took a look at your site – nice photos. And the new gallery you created in svManager seems to be working fine.
Your site uses html frames and Flash menus so it's always going to be a bit harder to change than a straightforward html/css site. However it doesn't look too difficult.
You'll need to create a new frames page similar to the existing ones and link to the new page from the menu. The quick solution would be to edit the link inside this page so it points to your new gallery. It would be something like
<frame src="nw/new/index.php" name="ed" frameborder="no" scrolling="no" id="ed">
A better idea for the longer term would be to change your folder structure. I would put the svmanager folder in your web root. New galleries created by svmanager will then appear as /svmanager/g1 etc. You can change the g1 name if you don't like it. You can put your frame pages wherever you like and link to the galleries with an absolute link:
<frame src="/svmanager/g1/index.php" name="ed" frameborder="no" scrolling="no" id="ed">
or with a relative link along the lines of:
<frame src="../svmanager/g1/index.php" name="ed" frameborder="no" scrolling="no" id="ed">
This structure would give you the option to upgrade all your galleries to SimpleViewer 1.8 fairly easily. You would just create a duplicate of an existing gallery in svManager using the same pictures and then change the link in the existing frames page to point to the new gallery instead of the old one.
Incidentally, SimpleViewer 1.8 uses larger thumbnails than the ones in your older galleries so you'll probably have to reduce the number of thumbnail rows. But that's really easy to do in svManager ;)
SimpleViewer Support Team.