Are you think about this?
HOWTO: upgrade Atahualpa to a new version
http://forum.bytesforall.com/showthread.php?t=8520
Manually upgrading wordpress is easy.
1) do a backup of the database
2) do a backup of the wp-content folder
3) in the wordpress root, delete all files and folders except the wp-content folder and the file wp-config.php
4) download the latest wordpress zip to your computer and unzip it
5) upload everything BUT the wp-content folder
6) go to
http://your domain.com/wp-admin and follow the directions
That's it