Wordpress upgrade mishap!

I am trying to upgrade to the new WP version 2.7 and this is what I get…my website has gone berserk…kaput! My fault though, I did not bother checking on the instructions first before proceeding with the supposedly easy upgrade.  My HOME page is mainly the problem and so goes with my PAGES and CATEGORIES, but the posts…thank goodness are still up and running with the correct URL typed in.
I even had my techy friends help me out until 4am! Well, my time while it was around 10 or 11 in the evening on their side.  I wanted to get into the latest version mainly because of the fabulous added features in it plus I was also thinking of making a new change again with a new theme and there were pretty good ones that can only be used with a newer version until I found a really nice look from Web 2.0 Wordpress Themes. I reverted to my old WP version and I can still use the nice themes out there, for free!