Re updating/upgrading - Here is a tutorial from Miraz Jordan, who literally wrote the book (I'm cutting and pasting this off a web design mailing list.)
unless you've done some unusual customisation on your blog there are 2
files that are crucial to retain: wp-config and the specific theme
folder that you've selected for your blog. That one will have a path
like: example.com/wp-content/themes/yourtheme.
All other files can be replaced.
Here's what I do to update my various blogs. It generally means that
the blog is offline / shows errors for a few minutes while I do the
update. Sometimes I create a plain HTM file with a 'site maintenance'
advisory and put that in place while I do things.
1] download the new version of WordPress and expand the zipped file.
2] sign in via FTP to my blog.
3] I open the wp-content, wp-admin and wp-includes folders into
separate tabs on my ftp software.
4] I open the wp-content folder so plugins and themes are also in their own tab.
5] I prefer to actually *delete* the old files first, but if you like
you can just replace them.
6] I upload the files from the new version into their appropriate
folders online.
7] If you put a holding page in place remove it again and upload the
index.php that belongs in the WordPress root folder.
8] Log in to the blog's Dashboard. If the database needs updating
it'll tell you and give you a button to press. Do that and wait a
moment. It should then tell you everything's OK.
9] Go to the Plugins section of your blog's Dashboard and see if any
plugins need updating.
