I always keep my sites upgrading if for nothing else it plugs security holes. As always before you start any upgrade do a complete backup of your site.
Here are the steps I take.
- Backup site as outlined in thread below
- Upgrade plugins
- Upgrade WordPress
- Upgrade Atahualpa manually
- Activate new Atahualpa version
- If all is OK you are done (other than images and paths as outlined in thread below.
- If site is broken switch back to version you were using and search for answer to problem and/or post question in forum.
For a complete set of instructions on upgrading take a look at this thread