"... If I open one in Preview it won't let me go to the next or previous,"
Don't open one in Preview. If the picture are in a folder do a command-a (select all). Then do a command-o (open file). They will all open in Preview and then you can hit the next button or use the arrow keys. In iPhoto you group photos together to make an event. Then you double click on an event and you can see all the photos. You can also set up a slide show as well. Post your iphoto questions in the iPhoto forums:
http://discussions.apple.com/category.jspa?categoryID=143
In the meantime stop down to your local book store and peruse the books available for Macs and Snow Leopard. Check out books by David Pogue who writes a tech column for the NY Times. They are light and easy to navigate through.