Edit: After more research on this, you might first look at juggledad's post about this sort of thing...
http://forum.bytesforall.com/showthread.php?t=21394
To do this right you need to
- Backup your DataBase
- Did I say backup your DataBase? If I forgot to mention it... BACKUP your DataBase!
- Perform an export of the theme's settings (since these are kept in the database, I don't know if this is really necessary, but I always feel better knowing I've got that data too)
- Backup your website's theme files - or at a minimum, backup any files you've added or customized
- Upgrade your version of WordPress
- Upgrade your version of Atahualpa - I MUCH prefer to do this manually, that way it's easier to recover if something goes nuts.
None of these steps are a guarantee everything will work out perfectly, there may be some additional 'tweaking' once the upgrades are performed. Some Plugins may or may not be compatible with the new version of WP or ATA, if that's the case, you'll have to go searching for replacements. This has happened to me a couple of times.
Depending upon what theme changes you made you may have some additional work within the Theme to get it to look exactly like your existing setup. I don't remember which version of ATA no longer allows PHP code in the 'Content ABOVE Loop' and 'The LOOP' options. I think that was back in 3.6.5 and if that's the case then you should not be affected by this since you're already running 3.6.7. Now that I think about it, I don't think it was an ATA 'issue', I think it was a WordPress requirement that no custom PHP code was allowed within the theme, but you can always modify the .PHP files directly (though you will have to remember to back them up if you upgrade).
I'd be very careful if you decide to have someone else do the upgrades for you. They will need access to your host back-end to perform proper backups. Once they are done (assuming they get it completed without issues), you would be well advised to change all your passwords associated with your hosting service, and database. juggledad and a few others on this site are highly capable of performing this upgrade for you but I don't know if they are wanting to assume the responsibility of that upgrade without compensation.